Making the mold: Take a rectangular baking pan and cut two wooden sushi sticks to the width of your pan. Place them at the bottom and cover with a piece of baking paper. This helps to create a mold for your chocolate shape with the filling.
Baking the frangipane: Evenly distribute the pistachio frangipane over the mold and bake for 12-15 minutes in a preheated oven at 185°C. Let it cool completely before proceeding.
Removing the mold: Carefully remove the frangipane from the mold and cut the sides loose if necessary. Place the frangipane on a rack with a baking sheet underneath to catch the chocolate.
Melting the chocolate: Melt the dark chocolate in a bain-marie or in the microwave (stir every 15 seconds to prevent the chocolate from burning).
Assembling: Pour the melted chocolate over the frangipane. Drizzle the pistachio butter on top and sprinkle with the coarsely chopped pistachios and sea salt flakes.
Setting: Let the bar set in the refrigerator. Once the chocolate is hard, you can break it into pieces for that delicious 'crack'.