• Bake the brownies according to recipe, in a 10 by 2 in [25 by 5 cm] heart shaped pan if desired.

For the filling

• Set aside cacao nibs. In a medium bowl, combine the peanut butter, sugar, butter, vanilla, and salt, and stir until completely smooth.

For the Ganache

• Place the chocolate in a small bowl. Heat the heavy cream in a small saucepan until it is simmering and just about to boil. Pour the cream over the chocolate, cover the bowl with plastic wrap, and let sit for 5 minutes. Remove the plastic and whisk until completely smooth. Let cool to room temperature.

To Assemble

• When the brownie has cooled, remove it from the pan and place it on a wire rack set over a parchment-lined sheet pan. Place the peanut butter filling on top and use an offset spatula to smooth the peanut butter. Sprinkle the cacao nibs evenly over the peanut butter. Chill in the freezer for 15 minutes. Remove the pan from the freezer, and pour the room-temperature ganache over the top of the peanut butter. Use an offset spatula to carefully smooth it over the top of the bars if needed. Let the bars sit until the chocolate is set. Cut the brownie into pieces. Store in an air-tight container in the refrigerator for up to 3 days.