This is how you use up leftovers the right way. Sweet, jammy onions. Tender, stout braised beef. Melty Fontina on thick, buttery sourdough that actually holds up under the weight of all of it. This open-faced sandwich might be the best leftover meal we’ve ever made, and we don’t say that lightly.
The thing that makes it so damned good? We don’t rush the onions. Forty minutes, low and slow, deglazing with water every time the pan threatens to burn… and what comes out the other side is a deep, sweet jam that you’ll want to spoon onto everything. Pile on the leftover shredded Braised Beef Shanks, blanket the whole thing in Fontina, and slide it under the broiler until it bubbles and browns at the edges, and it may be the best bite you’ve had all year.
In France, this style of open sandwich is called a tartine: thick, rustic bread with toppings layered on top so that every ingredient actually shines. And really, it may be our favorite way to use leftovers from our Braised Beef Shanks, from here on out.
🔪 Ingredients for Open-Faced Braised Beef Sandwiches
The Bread Base
- Thick sourdough or country loaf slices — sturdy crumb holds toppings without collapsing
- Salted butter — room temperature for easy spreading
The Beef & Onion Layer
- Yellow or sweet onions — thinly sliced for even caramelizing
- Pinch kosher salt
- Water — used to deglaze and develop natural onion sweetness
- Stout and Coffee Braised Beef Shanks — A quick skillet reheat gives the braised beef a little crust on the edges. It’s a tiny step that makes the sandwich taste like it came out of a pub kitchen instead of the leftovers container.
The Cheese & Finish
- Fontina cheese — shredded on the largest holes of a box grater for proper melt
- Fresh parsley leaves
- Freshly cracked black pepper
Equipment
- Cast iron skillet
- Wooden spoon
- Box grater
- Baking sheet
- Oven broiler (a kitchen torch works too)
📝 How to Make an Open-Faced Braised Beef Sandwich
1. Caramelize the Onions
Heat butter in a skillet over medium-low heat. Add sliced onions and a pinch of salt.
Cook slowly, stirring every few minutes. As the onions soften and moisture evaporates, browned bits will form on the bottom of the pan. Add a tablespoon of water whenever the fond begins to darken too quickly, scraping the pan clean each time.
Continue this process for 30–40 minutes until the onions are deep brown, glossy, and jam-like. The onions should smell sweet and look like onion jam—not pale, not burnt.
Set aside.
2. Toast the Bread
Spread softened butter generously on both sides of each bread slice.
Heat a clean skillet over medium heat, then place the bread directly in the pan.
Cook 2–3 minutes per side until deep golden brown and crisp. The crust should feel firm and sound crisp when tapped. Pan-toasting creates a fat barrier that keeps the sandwich from getting soggy.
3. Build the Sandwich
Place the toasted bread on a heatproof surface. Layer the sandwich in this order:
- Spread a thick layer of caramelized onions.
- Pile the shredded braised beef high in the center.
- Cover with a mound of shredded Fontina cheese, letting some fall over the edges.
4. Melt the Cheese
Preheat the oven broiler to high. Place the assembled sandwiches on a baking sheet and position them on the top rack of the oven.
Broil for 2–3 minutes, watching closely, until the Fontina melts and begins to bubble and lightly brown. The cheese should melt smoothly and drape over the beef with a few golden spots forming on top.
Remove immediately and serve while the bread is still crisp.
Optional Torch Method: If you have a kitchen torch, you can melt the cheese directly on the assembled sandwich instead of using the broiler. Hold the flame about 3–4 inches from the cheese and move it in small circles until the cheese is melted and lightly browned.
5. Finish & Serve
Transfer the sandwiches to a board, garnish with parsley, and finish with freshly cracked black pepper.
Serve immediately while the bread stays crisp and the cheese is molten.
What Is a Tartine?
A tartine is simply the French term for an open-faced sandwich served on thick slices of rustic bread. Instead of stacking ingredients between slices, everything sits on top so the bread stays crisp and the toppings stay balanced.
This braised beef version leans heavier and heartier than the café versions you might see with avocado or smoked salmon.
🔄 Substitutions & Variations
- Cheese swap: Gruyère works beautifully here.
- Bread swap: Thick ciabatta or rustic boule slices work well.
- Add acidity: A smear of whole-grain mustard under the onions adds balance.
- Add greens: Peppery arugula adds freshness if serving immediately.
💡 Meat Nerd Tips
- For extra crust, press the bread lightly into the skillet while pan-toasting. That full contact creates a better moisture barrier. And use a good loaf of bread. Thin soft ‘sandwich’ bread will get soggy.
- Don’t rush the onions. Proper caramelization builds the flavor foundation.
- Warm the braised beef before assembling so the cheese melts evenly and every bite is warmed through. If your braised beef still has excess liquid, simmer it briefly to reduce before assembling the sandwich. Too much moisture will soften the bread.
- Thickly shred the cheese. Fine shreds melt too quickly and can separate.
🍽️ What to serve with these braised beef tartines
This open-faced beef sandwich works well with simple sides that cut the richness:
- Bitter greens salad with vinaigrette
- Crispy roasted potatoes
- Pickled vegetables
A stout or porter pairs naturally with the braised beef.
🧊 Leftovers & Reheating
This sandwich is best assembled fresh.
To prep ahead:
- Store caramelized onions up to 4 days refrigerated
- Store shredded braised beef 3–4 days refrigerated
Reheat the beef in a skillet before assembling, and toast fresh bread in butter before making fresh tartines.
If you still have braised beef left, try it piled onto Irish Nachos, folded into Creamy Mac and Cheese, or baked into Braised Beef Hand Pies.
Have you tried this recipe? Do us a favor and rate the recipe card with the ⭐ ⭐ ⭐ ⭐ ⭐ and drop a comment to help out the next reader.
Open-Faced Braised Beef Sandwich with Caramelized Onions & Fontina
Recommended Equipment
- Wooden spoon
- Box grater
- Baking sheet
- oven broiler
Ingredients
- 2 thick slices sourdough or country loaf about 1 inch thick
- 4 tablespoons salted butter softened
- 2 large yellow onions thinly sliced
- pinch kosher salt
- water as needed for deglazing
- 1 cup stout-braised beef shanks shredded and warmed slightly
- 1 cup Fontina cheese thickly shredded (largest holes of a box grater)
- fresh parsley leaves
- freshly cracked black pepper
Instructions
Caramelize the Onions
- Melt 2 tablespoons butter in a skillet over medium-low heat. Add sliced onions and a pinch of salt.
- Cook slowly, stirring every few minutes, until onions soften and begin to brown.
- When browned bits form on the bottom of the pan, add about 1 tablespoon water and scrape the pan clean with a wooden spoon.
- Repeat this process for 30–40 minutes until the onions are deep brown, glossy, and jam-like. The onions should smell sweet and resemble onion jam.
- Set aside.
Toast the Bread
- Spread softened butter generously on both sides of the bread slices.
- Heat a skillet over medium heat and place the bread directly in the pan.
- Cook 2–3 minutes per side until deep golden brown and crisp.
Assemble the Sandwich
- Place toasted bread on a heat-proof surface or baking sheet or use the same cast iron pan.
- Spread a thick layer of caramelized onions over the bread.
- Pile shredded braised beef high in the center.
- Top with shredded Fontina cheese, letting some strands fall loosely over the edges.
Melt the Cheese
- Preheat the oven broiler to high.
- Place the assembled sandwiches on a baking sheet and position them on the top rack.
- Broil 2–3 minutes, watching closely, until the cheese melts and begins to bubble and lightly brown.
Garnish & Serve
- Transfer sandwiches to a board.
- Finish with parsley and freshly cracked black pepper.
- Serve immediately while the bread stays crisp and the toppings are hot.
Notes
- Pan-toasting the bread in butter creates a protective crust that keeps the sandwich from getting soggy once the onions and beef are added.
- Fontina melts smoothly and evenly, which is why it works well here. Gruyère is a good substitute if needed.
- If your braised beef has excess liquid, warm it gently and allow any extra moisture to cook off before assembling the sandwich.
- Broiling melts the cheese quickly while keeping the bread crisp. Keep a close eye on it so the cheese bubbles and lightly browns without separating.
Nutrition
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Quick Summary – Open Faced Braised Beef Sandwiches
This open-faced braised beef sandwich starts with butter-toasted sourdough that creates a crisp base. Slow caramelized onions add sweetness, leftover stout-braised beef provides rich savory depth, and shredded Fontina melts over the top for a bubbling finish. Because the bread is pan-fried first, it stays crunchy even under the weight of the toppings, making this one of the best ways to turn leftover braised beef into a fast second meal.
❓ FAQs
Sturdy rustic bread, like sourdough or a country loaf, works best. It holds toppings without becoming soggy.
Yes. Any tender shredded beef works well, but avoid overly saucy meat.
Fontina and Gruyère melt smoothly without separating into oil.
Pan-toasting creates a crisp fat barrier that prevents moisture from soaking into the bread.
You can prep the onions and beef ahead of time, but assemble and melt the cheese just before serving.
