Creamy Pesto Pasta

I'm going to try to post some of my recipes on my blog, as I make them throughout the week.
I have a few from this week. I'll start with this one. Inspired by a friend's facebook post :)
One day this week, I forgot to thaw out meat for supper, so this was vegetarian.
Variations in vegetable could include asparagus or peas. Chicken or shrimp (or anything you like) would also be a good protein to add!

Creamy Pesto Pasta
16 ounces whole wheat thin spaghetti
2 Tbs olive oil
1 tbs butter
1 small onion, chopped
5 minced garlic cloves
2 Tbs All-purpose flour
2 cups fat free milk
salt/pepper to taste
3/4 cup parmesean cheese (I used Kraft from the shaker, but you can use any variety, you could also use romano cheese instead)
1 cup prepared pesto (I used Tastefully Simple tomato basil pesto)
1 pound meat (shrimp or chicken, IF you want)
2 cups sliced mushrooms (i used canned)
2 tomatoes diced
4 cups broccoli steamed

Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.

Heat olive oil in a large skillet over medium heat. Saute onion until tender and translucent. Stir in garlic and butter, and saute until garlic is soft and fragrant, about 1 minute. Dissolve flour in milk, then stir in. Season with salt and pepper, and simmer 4 minutes, stirring constantly. Add cheese, and stir until melted. Stir in pesto. Add shrimp, mushrooms and tomatoes and broccoli. Cook 4 minutes, or until heated through. Toss with pasta until evenly coated.