Spinach and Artichoke Pasta

I have no idea where I got the original version of this recipe.  It's a printout in my recipe binder, not from the internet, just from a Word document.  No documentation.  I'm sure I pulled it off the internet somewhere...At any rate, I've tweaked it a bit, as usual!

Spinach and Artichoke Pasta

1/2 lb. dry pasta (rigatoni, rotini, bowties, etc.)
2 T. butter
1 medium onion, diced
1 cup sliced mushrooms
3 cloves garlic, minced
1 8-oz package neufchatel cheese (light cream cheese)
1/2 cup milk
1/2 cup light sour cream
Juice of 1/2 lemon
1 pinch red pepper flakes
1/2 tsp. salt
1/4 tsp. pepper
1 14-oz can artichoke hearts, chopped
1 10-oz box frozen spinach, thawed, with as much water squeezed out as possible
12 oz. sweet Italian sausages, previously cooked, sliced into 1/4" rounds

 Cook pasta in salted water to al dente, according to package directions.  Drain and set aside.  While the pasta cooks...

In a large skillet, melt butter over medium heat.  Add onions and mushrooms, sauteeing until onions are soft.  Add garlic and continue cooking just until garlic is fragrant.  Add neufchatel cheese and cook until melted.  Add milk, sour cream, lemon juice, salt, pepper, and pepper flakes.  Stir to combine.  Stir in artichokes, spinach, and sausage; continue cooking until spinach is heated through. 

Add drained pasta, toss, and add additional salt and pepper to taste before serving.