Set a rack in the middle of the oven and preheat to 375 degrees F. Lightly grease a 9-inch round cake pan. Line it with a disk of parchment paper or buttered waxed paper. Melt the chocolate and butter in the top of a double boiler over barely simmering water or in a small bowl set over a saucepan of just-simmering water. Remove from the heat.
Put the flour, cornmeal, sugar, chile powder, baking powder, and salt in a large bowl and stir together with a whisk. Stir in the eggs and buttermilk, then stir in the chocolate mixture. Spread the batter evenly in the prepared pan. Bake for 20 minutes, or until set and a tester comes out clean. Cool in the pan on a wire rack. Break the corn bread into 1-inch chunks. Spread in a shallow 2-quart baking dish.
Preheat the oven to 300 degrees F. Melt the chocolate in the top of a double boiler over barely simmering water or in a small bowl set over a saucepan of just-simmering water. Remove form heat. In a medium heavy-bottomed saucepan, combine the milk, cream, and 1 tablespoon of the sugar and bring to a scald. Meanwhile, put the remaining sugar and the egg yolks in a large bowl and whisk just to blend. While gently whisking the yolks, drizzle in the hot cream mixture so the yolks are gradually warmed up. Whisk in the melted chocolate.
Using a fine sieve, strain the custard over the corn bread chunks. Wiggle the chunks around so they are well soaked. Place the baking dish in a roasting pan and add enough hot water to come halfway up the sides of the dish. Bake for 40 minutes or until the custard is set.