Preheat oven to 425ºF. Generously butter the inside of 2 (5 ½ oz.) ramekins; set aside. In a medium mixing bowl, combine egg yolk, egg and sugar. Whisk until light, lemon colored and foamy; set aside.
In a medium pot filled with a little bit of water, place a bowl over (double boiler or Bain Marie). Place chocolate and butter; cook until melt, stirring occasionally, about 2 minutes. Pour chocolate mixture into egg mixture and whisk until well combined.
Add cocoa powder to egg mixture by using a fine mesh sieve over and tap or rub spoon until powder has passed through; stir until combined. Repeat with flour; stir until mixed. Add fleur de sell and stir until all the ingredients are very well combined.
Fill up each ramekin about 1/3 of batter. Spoon caramel sauce in each and cover with the rest of the batter. Place ramekins on a baking sheet lined with a silicone mat. Bake to the preheated oven for 12 minutes.
Remove from the heat and let them rest for 4 minutes. Loosen the edges from the ramekin with a knife. Invert each cake onto a plate and dust with confectioners’ sugar; garnish with raspberries and serve immediately.