Cook and drain the pasta while you make the sauce.

Sauce: In a saucepan, add butter and chopped onion. Cook, stirring frequently so the onion and butter will not burn.

When onion is tender, whisk in the flour and cook for one minute.

Add in the milk while whisking and bring the mixture to a boil.

Add salt, pepper, garlic powder and dried parsley. Simmer to thicken.

Add the parmesan cheese and the drained mushrooms. Stir to combine and melt the cheese.

After the pasta is cooked to your desired tenderness, drain and place back in the empty pot.

Add the sauce to the pasta and stir to combine.

Add the bacon crumbles and stir.

Serve immediately with extra parmesan cheese and bacon crumbles on top, as desired.