Preheat the oven to 350°F. Butter and flour a 13x18x1-inch sheet pan. Line with foil or parchment that hangs over the sides for ease in getting them out (butter the foil/parchment).
MAKE THE BROWNIES:
In a heatproof, medium-bowl set over a saucepan of simmering water, heat the butter, and chocolates and whisk until melted and smooth; cool slightly.
In a large bowl, whisk together the sugar, eggs, espresso powder and vanilla. Stir the egg mixture into the slightly cooled chocolate mixture. Cool to room temperature.
In a medium bowl, whisk together the flour, baking powder, and salt, then stir it into the batter. Pour the brownie batter into the prepared baking pan and smooth the top with a rubber spatula.
Bake for 25 to 35 minutes, or until a toothpick inserted into the center comes out clean with a few crumbs attached; do not overbake as you want them to be fudgy! Let the brownies cool completely, then cover tightly and chill for several hours or overnight. Chilled brownies are easier to cut. Invert the chilled brownie pan onto a large cutting board, peel off the foil or parchment. Use a 2-inch heart cookie cutter to cut out as many hearts as you can.
DIP THE BROWNIES:
Decide what you want to dip the brownies in. If you dip in chocolate, melt chocolate chips in the microwave with a teaspoon of shortening. Stir until smooth. Alternately, you can melt some colored melting wafers. Brush crumbs off of the top of the brownie and hold onto the sides toward the bottom. Dunk the tops into the melted chocolate and place on waxed paper to dry (chocolate-side-up). Sprinkle festive decor on top, if desired.
Notes
Nutritional information does not include the dipping chocolate.