Preheat the oven to 325°F/165°C. In a medium saucepan, combine 3⁄4 cup (149 g) of the sugar, the water, and corn syrup. Use a wet paper towel to wipe down the sides of the pot and have a cup of water with a pastry brush nearby. Bring the mixture to a vigorous boil over high heat. If sugar crystals form on the sides of the pan, brush them down with the wet pastry brush. When the sugar syrup begins to take on a golden hue along the edges, reduce the heat to low so it doesn’t cook too quickly. Continue to cook, shaking the pan frequently to distribute the cooked sugar, until the caramel has a dark golden, almost orange color, then immediately remove the pan from the heat and pour the caramel into the bottom of a 9-inch (23 cm) cake pan. Let the caramel sit until it cools down and becomes fairly firm.

In a large bowl, whisk the eggs to break them up. Add the remaining 1 3⁄4 cups (347 g) sugar and whisk until well combined; set aside.

In a medium saucepan, combine the milk and cream and cook over medium-high heat until they start to steam. Remove from the heat, add the cocoa powder, and whisk well, scraping down the sides of the saucepan to break up any small pockets of cocoa, until all the cocoa has dissolved into the milk.

While whisking, pour the hot milk mixture into the eggs in a slow, steady stream to temper the eggs. Add the almond extract and whisk well to combine.

Pour the custard base over the caramel in the cake pan, and put the filled cake pan into a baking pan at least 1⁄2 inch (12 mm) taller than the cake pan. Fill the outer pan with about 3⁄4 inch (2 cm) of water, then cover the whole thing with aluminum foil. (Make sure the foil is pulled tight and won’t sag over the flan.)

Bake for 1 hour and 30 minutes, until the flan is just set but still looks wet and jiggles when the pan is moved. (You can touch the top of the flan very gently with your finger to make sure that it is set; some of the custard may come off on your finger, but it will be thick, not liquid.) Keep the flan in the water bath and set aside to cool; the residual heat of the water will continue to cook the flan, and it will set as it cools. Once the flan cools to room temperature, refrigerate it for at least 3 hours to firm up.

To unmold the flan, run a paring knife between the sides of the flan and the pan, then place a large serving plate upside down on top of the cake pan and flip the flan onto the plate. (The plate should have a raised edge and be big enough to hold any caramel that slides off the top of the flan and falls down the sides.) Heat the bottom of the pan very quickly with a kitchen torch or soak a kitchen towel in very hot water, wring it out, and place on the bottom of the pan to loosen the caramel. Gently remove the pan. If any of the caramel has solidified into glasslike pieces, remove them from the flan and discard. Slice and serve.

Make Ahead: The baked flan can be kept in the refrigerator for up to 5 days.