Place potatoes in a saucepan and cover with water. Bring to a boil. Reduce heat; cover and cook for 15-20 minutes or until tender. Meanwhile, cut the tips off asparagus spears; set aside for garnish. Cut stalks into 1-in. pieces; place in a saucepan and cover with water. Bring to a boil. Reduce heat; cover and cook for 18-20 minutes or until tender. Drain asparagus and place in a food processor or blender. Cover and process until pureed; set aside. Drain potatoes; mash and set aside.
In a large saucepan, melt 1 tablespoon butter; whisk in flour until smooth. Gradually stir in cream. Bring to a boil; cook and stir for 2 minutes or until thickened. Stir in asparagus pieced, mashed potatoes, salt and pepper. Transfer to a greased shallow 1-1/2 quart baking dish. Top with reserved asparagus tips.
Melt remaining butter; lightly brush some over top. Toss bread crumbs, Parmesan cheese and remaining butter; sprinkle over casserole. Bake, uncovered, at 350° for 25-30 minutes or until lightly browned.