Preheat oven to 350°F. Line two 12-cup regular size muffin pans with 24 of the Valentine themed baking cups.
In a small bowl or cup, stir together milk and vanilla. In a separate bowl, sift flour and baking powder together.
Set electric mixer to medium, beat butter and sugar until creamy. Add flour to butter mixture alternately with milk. Beat on low speed until blended.
In a separate bowl, beat egg whites at medium speed until stiff peaks form; gently fold into batter. Fill baking cups about two-thirds full.
Bake at 350°F for 18-22 minutes or until a wooden toothpick inserted in center comes out clean. Cool in pans for about 5 minutes, then remove to wire racks. Cool about 20 minutes.
While the cupcakes are cooling, bring 1 cup of water to a boil. In a small bowl, pour boiling water over Jell-O. Mix until dissolved.
Using a toothpick, poke each cupcake several times. Spoon one tablespoon of the jello mixture over each cupcake. Return to wire racks. Cool completely before frosting.