Heat oven to 350 degrees F. Grease and flour an 8" square baking pan. In a medium bowl, stir together flour, sugars, cocoa, baking soda and salt. Add water, oil, vinegar and vanilla; beat with a whisk until smooth. Pour batter into prepared pan. Bake for 18 to 20 minutes or until wooden pick inserted in center comes out clean. Cool 10 minutes; remove from pan to wire rack. Cool completely. Transfer to cutting board. Using 3 1/4-inch heart-shaped cookie cutter, cut cake into four pieces. Spread chocolate frosting on top of two pieces. Place remaining two hearts on top.

For the Chocolate Frosting:

Place 1 tablespoon butter in a small, microwave-bowl.  Cook on high (100 percent power) for 20 seconds or until butter is melted. In a separate bowl, stir together the powdered sugar and cocoa. Add to butter mixture alternately with the milk.  Stir in the vanilla extract. Makes about 1/3rd cup frosting.