Preheat oven to 400°F. Lightly coat a 9x13-in. rimmed baking sheet with cooking spray. Whisk together flour, cocoa, granulated sugar, baking powder, baking soda, and salt in a large bowl.
Add egg and buttermilk, and whisk until just combined (some lumps are okay). Fold in chocolate chips and melted butter to combine. Spread batter evenly on prepared rimmed baking sheet. Bake until springy to touch, 12 to 15 minutes. Let cool completely.
Cut several hearts out of parchment paper. Place the heart cutouts on the cooled hotcake, and dust lightly with confectioners' sugar. Carefully remove cutouts. Cut into squares and serve with maple syrup and fresh berries, if using.
