1. Preheat the oven to 350°F.2. Melt the butter and 150g of chocolate in a double boiler.3. Break the chocolate into pieces and melt in a double boiler, stirring until smooth.4. Beat the butter and sugar until light. Add the eggs one at a time, beating after each addition.5. Add the melted chocolate and mix. Add the cardamom, salt, flour, and baking powder; mix slowly.6. Butter and flour individual molds. Fill halfway with batter and place a square of remaining chocolate in the center.7. Divide the remaining batter among the molds and bake for 15 minutes.8. Remove from the oven, unmold, and serve immediately.