Heat oven to 375 degrees. Prepare muffin batter as directed on package; spoon into 24 mini muffin pan cups sprayed with cooking spray. Press 1 each Velveeta cube and hot dog slice into batter in center of each muffin cup. Bake 10-12 minutes or until golden brown. Cool 5 minutes be- fore removing from pan. Serve warm with mustard. Ideal to serve to little kids. May substitute turkey franks or 12 halved classic mini dogs or spicy mini smokies for the hot dog pieces.