Preparation

Make the custard

• Whisk together the sugar, flour, and salt in a 6- to 8-quart saucepan. Whisk in the milk, Kahlúa, and espresso. Bring the mixture to a boil over medium-low heat and cook until thickened, whisking constantly; it will take about 20 minutes.
• In a stand mixer fitted with the whisk attachment, beat the egg yolks on medium-high speed until smooth, about 2 minutes. With the mixer running, gradually pour in 2-1/2 cups of the milk mixture and mix until incorporated. Pour the yolk-milk mixture into the saucepan, whisking constantly.
• Cook over low heat, whisking constantly, until the mixture begins to thicken, about 10 minutes. Remove from the heat and stir in the vanilla. Pour the custard through a fine-mesh strainer into a large bowl, pushing with a spatula if necessary. Press a piece of plastic wrap directly on the surface of the custard to prevent a skin from forming. Refrigerate overnight.

Bake the cake

• Position a rack in the center of the oven and heat the oven to 325°F. Butter and flour a 9×13-inch cake pan or glass dish.
• Sift together the flour, sugar, cocoa powder, baking soda, baking powder, and salt into the bowl of a stand mixer fitted with the paddle attachment. With the mixer on low speed, pour in the oil, eggs, vanilla, espresso, and milk. Increase the speed to medium and mix until fully incorporated, scraping down the sides as needed, about 2 minutes.
• Pour the batter into the prepared pan and bake until a toothpick inserted in the center comes out with a few moist crumbs, about 45 minutes.
• Remove from the oven and let cool completely on a rack. Invert the cake onto a cutting board and cut into 2-inch cubes.

Make the candied peanuts

• Combine nuts, cinnamon, cayenne, and salt in a medium bowl. Toss to combine. Add more spices to taste, if desired.

Whip the cream

• In a stand mixer fitted with the whisk attachment, combine the cream, sugar, Kahlúa, and cinnamon. Beat on medium speed until soft peaks form. Transfer the whipped cream to a piping bag fitted with a 1/2-inch plain tip or a large zip-top bag and snip off a corner.

Assemble

• 勺子足够的奶油4-quart蛋糕碗make a 1/2-inch layer. Place some of the cake cubes on top of the custard. Top with more custard. Pipe the whipped cream in several spots around the edges of the bowl. Top with more cake cubes and the remaining custard. Pipe the whipped cream in several spots around the edges of the bowl and add more cake cubes if there is room (there will be leftover cake). Spread the remaining whipped cream smoothly on top. Cover with plastic wrap and refrigerate the trifle for at least 1 hour or up to overnight.
• Before serving, top with the candied peanuts, if using, and the shaved Mexican chocolate.