Here is an easy (but maybe a little pricey) recipe that is good enough for a special occasion or company. I got it from allrecipes but adjusted it a little (this serves four):
Peppered Shrimp Alfredo
10 oz penne pasta
2 T olive oil
1 onion, diced
2 cloves garlic, minced
1 red bell pepper, diced
1/2 pound portobella mushrooms, chopped
1 lb medium shrimp, peeled & deveined
16 oz jar classico red pepper alfredo sauce
1/2 c grated romano chees
1/2 c cream
1 tsp cayenne
salt & pepper
1/4 c chopped parsley
!. Cook pasta and drain.
2. Meanwhile, melt butter together with the olive oil in a saucepan over med heat. Stir in onion, & cook till softened & translucent, about 2 minutes. Stir in garlic, red pepper, & mushroom; cook over med-high heat until soft, about 2 minutes more.
3. Stir in the shrimp & cook until firm & pink, then pour in alfredo sauce, romano cheese, & cream; bring to a simmer, stirring constantly until thickened, about 5 minutes. Season with cayenne, salt & pepper to taste. Stir drained pasta into sauce and serve sprinkled with parsley.