Preheat the oven to 350°F (175°C).

Line two baking sheets with parchment and draw small heart shapes as guides; then flip the parchment so the ink faces the pan.

In a medium bowl, whisk together the flour, cocoa, baking powder, and salt until evenly mixed.

In a large bowl, cream the 8 Tbsp of butter until smooth; add the brown sugar and beat until light and fluffy.

Mix in the egg and 1 tsp of vanilla until glossy.

Beat in the buttermilk and red gel food coloring; scrape down the bowl for even color.

Add the dry mix to the wet just until combined; do not overmix.

Transfer batter to a piping bag and pipe heart shapes onto the prepared sheets, spacing them 1½ inches apart.

Bake for 10–12 minutes until the tops are set and the edges look firm.

Cool on the pan for 10 minutes; then transfer cookies to a wire rack to cool completely.

Beat cream cheese, 5 Tbsp butter, and 2 tsp vanilla until smooth.

Gradually add powdered sugar and beat until fluffy.

Pair cookies by size, pipe a generous dollop of filling onto the flat side of one cookie, and top with its match.