Preheat your oven to 200°F/100°C.
To make the meringues, whisk the egg whites in an impeccably clean bowl on high speed to soft peaks. Slowly rain in the granulated sugar until combined. Then slowly add in the powdered sugar. You should only add about 1 tablespoon at a time of each of the sugars to allow the sugar to dissolve into the egg whites.
Whisk on high speed to stiff peaks.
Place a round piping tip in a large piping bag. You can leave off the piping tip but I prefer to use it for easier piping.
Scoop the meringue into the piping bag with a large spatula. Using a large cup to hold up your piping bag makes this step easier (see video).
Place silicone molds on a baking tray. Pipe the meringue around the molds, skipping every other mold so that your meringue is not touching. Continue until you have used all of the meringue. You should get 6 out of this recipe.
Use a spoon or small offset spatula to smooth and shape the meringue a bit, especially around the bottom of the dome to ensure that the meringue dome will have a flat bottom.
Grind the freeze-dried raspberries and sprinkle on top of the domes.
Bake at 200°F/100°C for 45 to 50 minutes. Leave the meringues in the oven with the oven turned off and the door propped slightly open until the meringues are completely cool. This can take about an hour but it is also fine to just leave them overnight.
To remove the meringues from the molds, VERY gently lift them off the molds. You may have to bend the molds slightly to get them out. Set the meringue molds aside while you make the sauce and filling.
To make the sauce, take about ⅓ of the berries that you are using and puree them in a blender or a food processor. Then strain the berries through a fine sieve to remove the seeds. Stir in a splash of the liqueur (if using). Refrigerate until ready to plate.
Whip the heavy cream to soft peaks. (You can whip to a stiff cream if you prefer but be very careful not to overwhip and make butter!) Stir together the jam and the liqueur. Gently fold the berries and the jam mixture into the whipped cream.
Use the filling to fill the meringue shells and serve on a bed of sauce. Assemble immediately before serving.