1. Place 1 cup asparagus and 1 cup broth in a blender; puree until smooth. Combine puree, remaining 2 cups broth, and 1 1/2 cups water in a medium saucepan; bring to a simmer (do not boil). Keep warm over low heat.
2. Melt butter in a large heavy saucepan over medium heat. Add onion to pan; cook 8 minutes or until tender, stirring occasionally. Stir in rice; cook 1 minute, stirring constantly. Stir in wine; cook 2 minutes or until liquid is nearly absorbed, stirring constantly. Add 1/2 cup broth mixture; cook 2 minutes or until the liquid is nearly absorbed, stirring constantly. Add remaining puree mixture, 1/2 cup at a time, stirring constantly until each portion of broth is absorbed before adding the next (about 30 minutes total). Stir in remaining 3 cups asparagus; cook 2 minutes.
3. Stir in 3/4 cup cheese, cream, salt, and pepper. Transfer risotto to a bowl. Serve with remaining 1/4 cup cheese.