Season and flour sirloin (shaking in a bag is easiest)
Saute onions and mushrooms until just softened.
Saute beef until just browned and crusty in oil; cook in batches if needed. (Use dutch oven or other oven safe pan and continue with same pan for baking to make less dishes).
Combine onions, mushrooms, stock, and Worcestershire into a dutch oven/casserole and bake at 300* for 2-3 hours; until beef is very tender.
15 Min. before serving fold in sour cream.
Notes
Serve over thick egg noodles.If thickening is needed dissolve 2 tblsp. cornstarch in 2-3 tblsp. water and at to bubbling sauce.
Put garlic and cream into a small saucepan over medium to medium low
heat.
Reduce cream to the point where it coats the back of a spoon.
Add the 4oz (1 stick) of butter and let melt.
Reduce heat to low and season with salt and pepper.
When mixture is no longer simmering, add cheeses very slowly while
constantly stirring mixture.
Remove garlic cloves and re-season with salt and pepper to taste.
Notes
Step 5 is very important. Do not add the cheese while the mixture is still simmering otherwise it will more than likely become grainy and un-appetizing. Also once the cheese is added to not bring back to a simmer. Cover with a lid and keep warm until serving..This sauce does not keep well. It is best to use all of it at once. Upon warming up the sauce will break.