an 8-cavity silicone heart mold (2 1/4-inch hearts); 4 medium round balloons; a 3-inch round cutter or ring mold
For the frozen hearts: Press the softened sorbet into 4 cavities of an 8-cavity silicone heart mold (2 1/4-inch hearts). Freeze at least 6 hours and up to overnight.
For the chocolate domes: Melt the chocolate in a double boiler. Once completely melted, let the chocolate cool to about 90 degrees F. The chocolate should still be melted and warm, not set.
Meanwhile, wash and dry the outside of 4 medium round balloons. Inflate the balloons so they are about 5 inches in diameter.
Holding onto the tied end of a balloon, dip it into the melted chocolate so that two-thirds of the balloon is covered in chocolate. Let the excess chocolate drip off. Place the balloon chocolate-side up in a coffee mug. Repeat with remaining balloons and chocolate. Let set at room temperature until hardened, 4 to 6 hours.
Once the chocolate is complete set and hard, very carefully pop each ballon with a knife and remove it from the interior of the chocolate dome. Place the domes open-side down on a warmed baking sheet and gently swirl to create a smooth edge. Transfer to a clean baking sheet lined with parchment paper. Store in a cool place.
For the white chocolate sauce: In a medium pot, heat the cream over medium-low heat until hot and bubbling around the edges. Immediately add the white chocolate chips and vanilla and whisk until the chocolate is completely melted and incorporated into the cream. Keep warm until ready to serve. You can make the sauce in advance and store in an airtight container in the refrigerator; reheat in a pot over low heat before serving, adding more cream if needed to thin it out.
For the assembly: In a medium mixing bowl, combine the crumbled sandwich cookies, brownies and fresh and freeze-dried raspberries. Gently toss to combine.
Line up 4 plates or wide shallow bowls (like pasta bowls). Place a 3-inch ring mold in the center of one of the plates and spoon in a quarter of the fruit and crumble mixture. Carefully remove the cutter. Repeat on the remaining plates. If you don't have a 3-inch cutter, neatly spoon the mixture into the center of each plate in a circle about 3 inches in diameter.
Make sure the white chocolate sauce is nice and hot and transfer to a measuring cup or small pitcher.
Working quickly, remove the raspberry sorbet hearts from the molds and place one onto each portion of the crumble mixture. Carefully cover each heart with a chocolate dome. Present to your guests and pour the hot chocolate sauce over the dome to melt and reveal the dessert.