Return the skillet used for the steaks to the stove top set over medium-high heat.

Add 1 tablespoon butter and the olive oil.

Once melted add the mushrooms and stir to coat. Spread in an even layer and cook undisturbed until the mushrooms are well browned on one side, about 5 minutes. Stir and continue cooking until the moisture is released and then evaporates and the mushrooms are well browned, about 3 minutes more.

Add the remaining 1 tablespoon of butter to the pan with the shallots and mushrooms.

Cook stirring frequently until softened, about 3 minutes.

Add the garlic and thyme leaves and sauté for 1 minute or until fragrant.

Gradually add the wine and stir to deglaze the pan while scraping up any browned bits on the bottom.

Continue cooking until almost all the wine has evaporated.

Stir the cornstarch into the beef stock then add the beef stock, mustard and Worcestershire to the skillet and bring to a simmer.

Continue to cook and stir until the sauce is slightly reduced, about 5 minutes.

Reduce the heat to low and add the cream. Heat gently for a few minutes or until the sauce thickens slightly and coats the back of a spoon.

Check the seasoning and add salt and pepper to taste. Add a splash of beef stock if needed for desired consistency.

Transfer the steaks to individual plates and pour any accumulated juices into the mushroom sauce. Stir to combine then spoon over the steaks and serve immediately.