1. Preheat the oven to 350°F.
 
2. Melt 150g of chocolate in a double boiler, stirring until smooth.
 
3. Beat the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition.
 
4. Add the melted chocolate and mix. Add the flour, cinnamon, and baking powder; mix slowly.
 
5. Butter and flour individual molds. Fill halfway with batter and place a square of chocolate in the center.
 
6. Divide the remaining batter among the molds and bake for 10 minutes.
 
7. Remove from the oven and serve immediately.