Combine the butter and granulated sugar in a large mixing bowl. Beat on medium speed until light and fluffy.

Add the egg and vanilla. Beat until well incorporated.

In a separate bowl, whisk together the flour, cocoa, baking powder, and salt.

Gradually add the dry mixture to the creamed mixture, mixing on the lowest speed. Mix until the dry ingredients are just incorporated.

Divide the dough in half and shape it into two discs. Wrap in plastic wrap and refrigerate for 1 hour.

Once the dough is chilled, preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper or a baking mat. Set aside.

Take one portion of dough out of the refrigerator at a time. On a lightly floured surface, roll the dough to 1/8-1/4 inch thickness.

Use a heart-shaped cookie cutter to cut out cookies and transfer them to the prepared baking sheet.

Bake the cookies for 9-10 minutes, then transfer them to a wire rack to cool completely.

Prepare the filling by combining the softened butter, half and half, vanilla, and salt in a bowl. Beat until combined.

Gradually add the powdered sugar until the filling is smooth. It should be slightly stiffer than cupcake frosting. Add pink or red food coloring until the desired color is achieved.

Transfer the filling to a piping bag fitted with a large round tip (or a freezer zip-lock bag with the corner snipped off).

Pipe the filling onto half of the cookies and top with the remaining cookies to create a cookie sandwich.