Preheat oven to 400°.
Cut tops off bell peppers; discard tops, seeds, and membranes. Cook peppers in boiling water 5 minutes; drain and set aside.
Heat a large nonstick skillet coated with cooking spray over medium-high heat. Add lamb; cook 6 minutes or until browned, stirring frequently. Drain and pat dry with paper towels. Wipe drippings from skillet with a paper towel.
Return lamb to pan; add broth and the next 6 ingredients (broth through salt). Bring to a boil; cover, reduce heat, and simmer for 10 minutes. Combine cornstarch and water, stirring well with a whisk. Add to lamb mixture; bring to a boil. Cook 1 minute, stirring constantly. Divide the lamb mixture evenly between peppers. Place stuffed peppers in an 8-inch square baking dish, and set aside.
Combine the potatoes and milk in a microwave-safe bowl, stirring well. Microwave at HIGH 2 minutes, stirring after 1 minute. Let stand for 2 minutes. Spoon warm potato mixture evenly over tops of stuffed peppers, and lightly coat the potato mixture with cooking spray. Combine the cheese and paprika; sprinkle over potato mixture.
Bake at 400° for 20 minutes or until potatoes are golden.