Cut asparagus into 1-inch pieces and steam about 2 minutes or until the asparagus is bright green in color. Drain and set to one side.
Cook pasta in boiling water according to package directions. Drain and set aside.
While the pasta is cooking, heat the half and half in a heavy pan on low heat while slowly adding the cheeses with flour, whisking until well blended. When the cheese is melted, add stir in the butter and fold in asparagus. Toss the pasta with the asparagus and sauce, and serve.