1. In a large, microwave-safe bowl, microwave two-thirds of the bittersweet chocolate for 30 seconds, then stir. Repeat until the mixture is smooth. Stir in the remaining chocolate until melted. Transfer 2 tablespoons to a heavy-duty resealable plastic bag and snip a small hole in one corner.
2. Pipe 12 small (2-inch) heart outlines onto a wax paper-lined cookie sheet. Refrigerate until set, about 5 minutes. Fold the strawberries into the remaining bittersweet chocolate. Divide among the heart outlines and carefully spread to fill in the hearts.
3. Repeat the melting technique above with the white chocolate. Pipe decorations onto the hearts. Let stand until set.
The hearts can be refrigerated in an airtight container for up to 1 week.