Heat a large skillet over medium heat and add olive oil and 1 tbs butter (if your grill is large enough, just use the indirect heat side to cook these a few minutes before you throw your steaks on). Swirl to coat the pan. Add the mushrooms, and cook, stirring often 10 to 15 minutes. Stir in the garlic and cook 2 minutes longer. Remove the mushrooms for the pan and reduce the heat to low. Sprinkle the thyme over the mushrooms Stir in the chicken stock and deglaze the pan. Add the remaining 1 tbs butter and melt. Stir the mushrooms back into the skillet and let the liquid thicken, 2 to 3 minutes. (Add a splash of brandy if you are feeling wild).