Prepare the Shells

1. Melt white chocolate with butter in a double boiler until smooth.
2. Spread the mixture into Silpat Mini Heart Mold using a brush.
3. Freeze for 5 minutes; repeat twice.
4. Leave the mold in the freezer while preparing the raspberry mousse.

Prepare the Raspberry Mousse

1. Rehydrate gelatin sheet in cold water for 10 minutes.
2. Heat raspberries with sugar in a saucepan to reduce water content.
3. Add softened gelatin sheet; mix well and let it cool.
4. Whip the whipping cream until stiff peaks form; then, fold in the raspberry mixture.
5. Beat egg whites until stiff peaks form; fold them into the raspberry and whipped cream mixture.
6. Chill the mousse.

Assembly

1. Remove the mold from the freezer.
2. Fill each heart-shaped cavity with raspberry mousse until the top.
3. Place the mold in the freezer until the mousse sets.
4. Spread a thick layer of the white chocolate/butter mixture on top to seal the hearts.
5. Freeze until the chocolate hardens.
6. Carefully unmold the hearts for a delightful Valentine's Day treat.