Crawfish Fettucine

4 tablespoons butter
1 small onion, diced
small package mushrooms, sliced (optional)
1 1/2 cups half and half
1 teaspoon flour
6 ounces Velvetta cheese, cubed
1 can Rotel, drained
1/2 cup grated parmesean cheese
1/2 teaspoon cayenne pepper
1 teaspoon Tony's
1 teaspoon salt
1 pound crawfish tails

Melt butter over medium heat and add onions, cook until soft and add mushrooms. Cook for about 2 minutes and add flour. Stir and cook down until flour is no longer clumpy. Add half and half and crawfish tails. Let simmer for 6-8 minutes, until the flour is completely cooked down. Add Rotel and Velvetta. Once Velvetta is melted, add cayenne pepper, Tony's and salt. Slowly add parmesean cheese. Let simmer for a few minutes until desired consistency is reached.
Serve over pasta.