Cook pasta following package directions. Rinse in cold water; drain well. Toss with olive oil in large bowl.
Combine Gorgonzola, milk, heavy cream, salt and pepper in food processor or blender. Whirl until well blended. Pour over pasta. Add red onion; toss gently to mix.
Line serving bowl with radicchio leaves. Spoon pasta in middle. Top with toasted walnuts. Makes 6 servings.