Preheat oven to 375 degrees F. Butter a 9-inch round cake pan and line the bottom with a disk of parchment paper.
Place chocolate in a double boiler over simmering water and stir until melted. Remove from heat and let cool slightly.
Whisk together the flour, cornmeal, sugar, chili powder, baking powder, and salt in a large bowl. Stir in the eggs and buttermilk and then stir in the melted chocolate. Scrape batter into the prepared pan and bake for 18 to 20 minutes. Cool in the pan on a rack.
Once the bread is cool, break into 1-inch chunks and spread in the bottom of a 2-quart baking dish.
Whisk together the sugar and yolks in a large bowl until pale. Whisk in the melted chocolate, milk, cream, and vanilla extract until combined.
Using a fine sieve, strain the custard over the bread chunks. Press on the bread chunks so that they are soaked in the custard mixture. Place the pan in a roasting pan and fill the roasting pan halfway with hot water. Bake for 40 minutes or until the custard is set. Remove and let cool on a rack for 30 minutes before serving. This is best served warm. Spoon into bowls and drizzle with the Hot Mexican Chocolate Sauce.
Bring heavy cream and cinnamon sticks to a simmer in a small saucepan. Remove from the heat and let steep for 15 minutes. Remove the cinnamon sticks, add the chocolate and sugar, and cook over low heat until the chocolate is completely melted. Stir in the almonds and transfer to a small pitcher. Keep hot.