How to Make It
In the bowl of a stand mixer fitted with the paddle, beat the butter and the 3/4 cup of confectioners’ sugar at low speed until well blended, then beat at medium-high speed until smooth and lightened, scraping down the side of the bowl, about 5 minutes. At low speed, add the flour, potato starch and salt and beat just until the dough comes together; it will be quite soft. Scrape the dough onto a sheet of parchment paper and pat 1 inch thick. Top with another sheet of parchment paper and roll out 1/4 inch thick. Transfer the dough to a baking sheet and refrigerate until firm, about 1 hour.
Meanwhile, line a baking sheet with parchment paper. In a small saucepan, combine the granulated sugar with 1/2 cup of water and bring to a boil. Add the chopped almonds and cook over moderately low heat, stirring occasionally, until the syrup is reduced by half and thick, about 15 minutes. Drain the almonds in a sieve. Spread on the prepared sheet in a single layer and let cool completely.
Preheat the oven to 350°. Line 2 more baking sheets with parchment paper. Using a 2-inch heart-shaped cookie cutter, stamp out cookies and arrange them 1 inch apart on the prepared sheets. Using a smaller heart-shaped cookie cutter, stamp out the centers of half of the cookies. Transfer the whole cookies to 1 prepared baking sheet and the cutout cookies to another. Gather all of the scraps and reroll between 2 sheets of parchment to stamp out more cookies. Scatter the candied almonds on top of the cookies with the centers cut out and press gently to help them adhere.
Bake the cookies for about 18 minutes, rotating and shifting the pans halfway through, until golden around the edges. Transfer to racks to cool completely.
Spoon a scant tablespoon of raspberry jam onto the whole cookies. Dust the cutout cookies with confectioners’ sugar and assemble the sandwiches; press gently to adhere.