Whisk the flour, baking powder, and salt together in a medium bowl. Set the dry ingredients aside while you prepare the butter mixture.

Beat the softened butter and granulated sugar for 2–3 minutes, until light and creamy. Add the room-temperature egg and vanilla extract, plus the almond extract if using, and beat until combined.

Add the dry ingredients to the butter mixture and mix just until a soft dough forms. Do not overmix, since too much mixing can make the cookies less tender.

Divide the dough into two portions, flatten each portion into a disk, wrap, and refrigerate for at least 1 hour. Chilling firms the butter and helps the heart shapes hold during baking.

Heat the oven to 350°F (175°C) and line baking sheets with parchment paper. Roll one dough disk on a lightly floured surface or between sheets of parchment paper to about 1/4 inch (6 mm) thick.

Cut the dough with a heart-shaped cookie cutter and transfer the shapes to the prepared baking sheets. Re-roll the scraps only once or twice, and chill the cut cookies briefly if the dough becomes soft.

Bake for 9–12 minutes, until the edges are set and just beginning to turn pale golden. Keep the centers light rather than deeply browned for a soft, delicate cookie.

Cool the cookies on the baking sheet for 5 minutes, then move them to a wire rack to cool completely. Do not ice warm cookies, because the icing can melt and slide off.

Whisk the confectioners' sugar, milk or cream, and vanilla until smooth. Tint the icing pink or red, spread or pipe it over the cooled cookies, and add sprinkles while the icing is wet.

Let the icing set before stacking or storing the cookies. Keep them in an airtight container at room temperature once the decoration is firm.