Preheat oven to 350°F. Grease and flour 2 (9-inch) round cake pans. Place paper baking cups in 2 standard-size muffin cups, or grease and flour 2 (4-oz.) ramekins.

Prepare the Red Velvet Cake: Beat butter with an electric mixer on medium speed until light and fluffy, about 3 minutes. Gradually add granulated sugar, beating until blended. Add eggs, 1 at a time, beating until blended after each addition. Beat in food coloring and vanilla.

Whisk together flour, cocoa, baking powder, baking soda, and salt; add to butter mixture alternately with buttermilk, beginning and ending with flour mixture. Beat at low speed just until blended after each addition. Fill muffin cups or ramekins three-fourths full. Divide remaining batter between prepared cake pans.

Bake in preheated oven until a wooden pick inserted in the center comes out with moist crumbs, 15 to 16 minutes for cupcakes and 20 to 25 minutes for cake layers. Cool cake layers and cupcakes in pans on wire racks 15 minutes. Transfer cake layers and cupcakes from pans to wire racks, and cool completely, about30 minutes. Wrap cupcakes in plastic wrap, and freeze 2 hours.

Prepare the Ice-Cream Layer: Line a 9-inch round cake pan with plastic wrap, allowing ends to extend over edge of pan to create handles. Remove cupcakes from freezer, and cut into 1⁄4-inch cubes. Place ice cream in a large bowl; beat at medium speed until soft but not melted. Gently fold cupcake cubes into ice cream. Spread ice cream into prepared pan. Cover and place pan in freezer until frozen, at least 3 hours or overnight.

Prepare the Frosting: Place water in a small microwavable bowl, and sprinkle with gelatin; let stand 5 minutes. Microwave on HIGH until gelatin melts and mixture is smooth, about 10 seconds. Let stand5 minutes.

Place cream, powdered sugar, and vanilla in a large bowl. Beat at medium-high speed until soft peaks form. With mixer on low, gradually add gelatin. Increase speed to high, and beat until stiff peaks form.

Assemble the cake: Place 1 Red Velvet Cake layer on a platter or cake stand. Using plastic wrap handles, remove Ice-Cream Layer from pan and place on top of cake layer. Top with remaining cake layer. Spread Frosting over sides and top. Loosely cover with plastic wrap, and freeze at least 2 hours.

Let stand at room temperature 20 minutes before serving. Top with blueberries, and serve immediately. Freeze any leftovers.