Melt 1 tbsp butter in a skillet over medium heat. Add shallot and garlic and cook until soft and translucent, 3-5 minutes.
Add remaining butter and allow to melt. When melted, add mushrooms and stir to coat. Cook, stirring frequently, until mushrooms soften and begin to exude liquid, about 5 minutes.
Add beef broth, wine, Worcestershire sauce, bay leaf, thyme and pepper. Bring to a simmer over medium-high heat, then reduce to medium-low and simmer until reduced by about half, 45-60 minutes. Taste and correct seasoning if needed. (A splash of soy sauce instead of salt adds another dimension and is an alternative if needed.) Remove bay leaf before serving.