Ingredients
¼ oz packet unflavored gelatin
4 cups milk
1 teaspoon vanilla essence
12 large egg yolks
1 cup sugar
6 tablespoons cornstarch
¼ teaspoon salt
5 tablespoons unsalted butter
½ cup semi sweet or dark chocolate chips
1 tablespoon instant coffee
1½ cup heavy cream
10 tablespoons unsalted butter, cut into pieces
1 ½ teaspoon sugar
½ teaspoon salt
1 ½ cups all purpose flour
6 large eggs
3 cups sugar
3 tablespoons light corn syrup

Preparation

1. Begin by preparing the cream filling. Sprinkle the gelatin over ¼ cup of cold water in a small bowl and let it soften (bloom).
2. Measure out the milk in a heavy bottom pan. Add the vanilla and bring a simmer over medium high heat. Once the milk starts to simmer, remove from heat and set aside.
3. Whisk the egg yolks, 1 cup sugar, cornstarch and ¼ teaspoon salt in a medium bowl until smooth. Gradually whisk one-third of the milk into the egg mixture to temper the yolks. Add rest of the milk and whisk together. Return the pan over medium heat and cook the mixture while constantly whisking the mixture.
4. Cook the custard till the mixture boils and thickens. This will take about 5 to 6 minutes. Continue cooking till the mixture turns into custard consistency. Remove the pan from the heat and stir in the butter, a tablespoon at a time. Add in the softened gelatin.
5. Microwave the chocolate chips for 30 seconds, stir and heat again in 30 second increment till the chocolate is fully melted and smooth. Dissolve the instant coffee in 2 tablespoons of hot water. Stir in the coffee and chocolate into ½ the custard filling. Keep the other half plain. Cover both the bowls with plastic wrap with the wrap touching the surface to prevent any film from forming on top and chill the custard for 2 hours.
6. When ready to fill the puffs, whip the heavy cream into soft peaks. Fold half of it into the vanilla filling and the other half into the chocolate filling.
7. Transfer each filling to a large pastry bag with a 1/4-inch tip and set aside.
8. Prepare the pastry puffs while the custard is cooling. Preheat the oven to 450F.
9. Bring 1 ½ cups of water, remaining butter, sugar and salt to a simmer in medium saucepan. When the butter melts completely, remove the pan from the heat and stir in the flour with a wooden spoon to make a paste. Return the pan to heat and cook stirring constantly till the mixture pulls from the side and turns shiny. Remove from heat and let cool slightly.
10. Transfer the paste to a stand mixer with the paddle attachment and start mixing on medium low speed for about a minute. Beat in the eggs, one at a time till fully incorporated.
11. Transfer the dough to a large pastry bag with a 1/2-inch tip. Line 2 baking sheets with parchment paper and pipe 1 1/2-inch balls of dough onto the paper. You should get about 40 plus dollops.
12. Smooth out any pointy tips of the piped dollops with a wet finger. Bake for about 15-20 minutes, till the dough is puffed. Lower the temperature to 350f and bake until the puffs are golden and feel light. Turn off the oven and keep the puffs inside for another 10 minutes or so. Remove the puffs to a cooling rack and let cool completely.
13. Assemble the croquembouche as close to serving time as possible. Fill half the puffs with chocolate cream and the other half with vanilla by piping the cream from the bottom. You can lightly push in the piping from the bottom and squeeze the filling till the puff feels pretty full. Take care to avoid overfilling so the custard doesn’t explode out of the puffs.
14. Let the filled puffs chill in the refrigerator for 30 minutes or so.
15. To assemble the puffs as a tower, you need to make the caramel. Mix the 3 cups of sugar, corn syrup and 1 cup water in a saucepan, cover and bring to a boil over high heat. Boil the syrup till it turns deep amber. Take care not to burn the caramel. Another way to do this is to use a candy thermometer and boil the syrup till it reaches hard candy stage.
16. Immediately dip the bottom of the saucepan in a large bowl of ice water for a few seconds to stop the cooking. Let cool for a couple of minutes. The syrup should still be quite liquidy.
17. Partially dip each filled puff into the caramel and let the excess drip off. Arrange the puffs around the circle. If the caramel hardens, microwave until soft, 45 seconds.
18. Fill the base circle with more puffs for stability, then continue building a conical tower of smaller circles.
19. Dip the tip of a fork into the caramel and wave it around the tower, letting the syrup fall in strands around it. If the syrup is on the liquidy side, the syrup might not form the web look you are after. Let the syrup cool slightly and drizzle it slowly so it will cling better to the puffs and create the web look.