Melt Chocolate and Butter: Melt the dark, milk, and white couverture with the butter in a microwave or saucepan. Start with 1 minute and add 30-second intervals if needed.
Mix Eggs and Sugar: In a bowl, mix two whole eggs and one egg yolk with granulated sugar.
Combine Chocolate Mixture and Egg Mixture: Add the melted chocolate and butter to the egg and sugar mixture. Mix until combined without overmixing.
Add Remaining Ingredients: Add honey, flour, cocoa, salt, and the remaining pieces of milk and white chocolate. Mix until just combined.
Prepare for Cooking: Pour the mixture into a buttered mold lined with parchment paper. Place the mold in the pressure cooker with a tripod stand and 500 g of water. Wrap the mold tightly with aluminum foil.
Cook: Cook in the pressure cooker on high heat. Once the valve shows the correct color, lower the heat and cook for 30 minutes.
Serve: Let the brownie cool before cutting into pieces. Serve with melted milk and white couverture drizzled on top.