In a medium sauce pan melt butter over high heat. Add onion and sauté. Add garlic and sauté as well.
Add sour cream and chipotle peppers and stir until it blends with the butter. Add rosemary.
Reduce heat add 1/4 cup of the Parmesan cheese. Stir until it melts and blends with the sauce.
Add mushrooms, season to taste and let the sauce simmer for about 7 minutes.
Turn heat off and add the rest of the cheese. Stir constantly until it melts.
You can either serve the pasta on a plate and pour some of the sauce on top or add the pasta to the sauce pan and toss it together to coat it with the sauce.
Serve and enjoy!
Recipe by What's Cooking Mexico at http://whatscookingmexico.com/2010/10/21/chipotle-alfredo-pasta/