These sparkly sandwich cookies look like little snowballs, with a bright red ribbon of raspberry filling in the middle.
Preheat the oven to 350°F. Line two baking sheets with parchment.
To make the dough: In a large bowl, beat together the butter, confectioners’ sugar, salt, and Fiori di Sicilia until smooth. Add the flour and mix just until combined.
Scoop teaspoon-sized balls of dough and roll them in sparkling sugar. Place the balls on the prepared baking sheets.
Bake for 12 to 14 minutes, just until the cookies begin to brown at their edges. Remove from the oven and let cool on the pan for 5 minutes before transferring to a rack to finish cooling completely.
To make the filling: Place the confectioners’ sugar and the freeze-dried raspberries in the bowl of a food processor. Process until the berries are powdered. Whisk the mixture through a mesh strainer to remove any lumps or seeds. Mix in the butter at low speed until everything is cohesive. Add the milk, a teaspoon at a time, until the filling's spreadable.
To assemble: Scoop a teaspoon of filling onto the bottom of half the cookies; sandwich with the remaining cookies, pressing gently.
