For the cake: Preheat the oven to 350 degrees F. Butter and lightly flour three 6-inch round cake pans.
Whisk together the flour, sugar, cocoa, baking powder, espresso powder and salt in a mixer bowl until well combined. Add the milk, oil, eggs and vanilla to the flour mixture and beat on medium speed until well combined. Reduce the speed to the lowest setting and carefully add 1 cup boiling water. Increase the speed to medium-high and continue to beat, about 1 minute (see Cook's Note).
Divide the batter among the prepared cake pans and bake until a toothpick inserted in the center comes out clean, about 30 minutes. Cool in the pans on a rack for 10 minutes, then turn out onto racks to cool completely.
For the dulce de leche filling: Whisk together the dulce de leche and heavy cream until well combined and smooth.
For the chocolate fudge filling: Combine the condensed milk, evaporated milk, cocoa powder and vanilla in a saucepan. Cook over medium heat, stirring constantly, until thickened, about 30 minutes. Transfer to a bowl and place in the refrigerator to cool and thicken.
For the chile pepper Swiss meringue buttercream: Meanwhile, place the egg whites, salt and 1 cup of the sugar in a heatproof mixer bowl set over a pan of simmering water. Whisk gently and constantly until the sugar is dissolved and the egg whites are hot, about 4 minutes. Remove from the heat. Beat with a mixer fitted with the whisk attachment at medium-high speed until thick and cool, about 5 minutes. Beat in the butter until the buttercream comes together.
Boil the chile peppers and remaining 3/4 cup sugar together for 10 minutes. Let the peppers cool slightly, then peel and remove the seeds. Pulse the peppers in a food processor until smooth, then press through a strainer to remove any chunks. Mix about 8 tablespoons of the pepper puree into the buttercream, or more to taste.
To assemble: Level off the tops of the cake layers with a serrated knife. Place one layer on a cake plate and spread with the dulce de leche filling. Top with another cake layer and spread with the chocolate fudge filling. Top with the remaining cake layer and frost the outside with the chile pepper buttercream. Serve immediately or let stand at room temperature for up to 2 hours.
The cake batter will have a very thin consistency once everything is mixed together.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.