Peppered Shrimp Alfredo

"Yummy shrimp in an Alfredo sauce, with portobello mushrooms and red peppers."
Ingredients 

Original recipe makes 6 servings
 12 ounces penne pasta
 1/4 cup butter
 2 tablespoons extra-virgin olive oil
 1 onion, diced
 2 cloves garlic, minced
 1 red bell pepper, diced
 1/2 pound portobello mushrooms, diced
 1 pound medium shrimp, peeled and deveined
 1 (15 ounce) jar Alfredo sauce
 1/2 cup grated Romano cheese
 1/2 cup cream
 1 teaspoon cayenne pepper, or more to taste
 Salt and pepper to taste

 1/4 cup chopped parsley