Melt 3 tablespoons of butter in a large skillet over medium heat.
Add mushrooms and shallots and saute for 4-5 minutes or until mushrooms are softened, making sure that the shallots do not burn.
Add flour and cook for 2 minutes.
Add the sherry and chicken stock to the skillet, 1/2 cup at a time, whisking until combined.
Add House Seasoning Blend; Cook for 10 minutes.
Add cream and cook for 2 minutes more.
Remove skillet from the heat and add remaining tablespoon of butter, whisking until smooth.
Slice filet mignon into thin strips, making sure to slice against the grain of the meat.
Pour sauce over pasta and arrange filet mignon slices on top.
Notes
Don't over cook the steak: I wouldn't recommend going beyond medium or medium-well at the most.
Use good quality sherry: Pick up a bottle of the best sherry you can afford. When you cook the sherry down, the flavor intensifies so you want the best flavor possible.
Try different types of mushrooms: I usually use crimini mushrooms but feel free to swap your favorites into this recipe.