Heat oven to 350 degrees.

In a medium frying pan gently cook mushrooms in 1 tablespoon butter, until softened. Remove from heat.

Melt 3 tablespoons butter in medium sauce pan. Whisk in flour, cook for 2 minutes stirring constantly. Gradually stir in milk, cook until mixture thickens, stirring constantly.

Add Velveeta and cook until melted, stirring frequently. Add chicken, mushrooms and Farfalle, stir until blended.

Spoon mixture into a baking dish. Top with cheddar and Fritos.

Bake 20 minutes or until heated through.