1 lb beef sirloin or tenderloin, thinly sliced
2 tbsp butter
1 tbsp olive oil
1 small onion, finely chopped
2 cloves garlic, minced
8 oz mushrooms, sliced
2 tbsp all-purpose flour
1 cup beef broth
1 tbsp Worcestershire sauce
1 tsp Dijon mustard
1/2 cup sour cream
Salt, to taste
Black pepper, to taste
1 tbsp chopped parsley, optional
Heat butter and olive oil in a skillet over medium-high heat
Cook beef until browned, then remove from the skillet
Add onion and cook until softened
Add garlic and mushrooms, then cook until mushrooms release moisture and brown
Sprinkle flour over the mixture and stir for 1 minute
Slowly pour in beef broth while stirring
Add Worcestershire sauce and Dijon mustard
Simmer until sauce thickens
Reduce heat to low
Stir in sour cream
Return beef to the skillet
Season with salt and black pepper
Garnish with parsley if desired