Peanut and Salted Caramel Stout Cake

STEP 1: PREPARE THE PANS

Heat the oven to 325°F. Grease three 8-inch round cake pans with butter and line the bases with parchment.

STEP 2: MAKE THE STOUT BASE

Warm the alcohol-free stout and cubed butter in a large saucepan over low heat until the butter melts. Take off the heat and whisk in the Dutch-process cocoa powder and sugar until smooth. Let the mixture cool for 10 minutes so it is warm rather than hot.

STEP 3: ADD THE EGGS

Whisk the sour cream, eggs and vanilla extract together, then whisk into the stout mixture until evenly combined.

STEP 4: ADD THE DRY INGREDIENTS

Whisk the flour, baking soda and fine salt together, then whisk into the wet mixture until just smooth. The batter will be thin and pourable. That is correct, so do not add more flour.

STEP 5: BAKE THE SPONGES

Divide the batter equally among the pans and bake for 30–35 minutes, until risen and a skewer comes out with a few moist crumbs. Do not raise the heat to speed this up; the wet batter needs the moderate temperature to set through the middle.

STEP 6: COOL THE SPONGES

Cool the sponges in their pans for 15 minutes, then turn out onto wire racks and cool completely, at least 1 hour. Warm sponges will melt the buttercream and the layers will slide.

STEP 7: MAKE THE SALTED CARAMEL

Combine the sugar and water in a heavy saucepan over medium heat, stirring only until the sugar dissolves. Boil without stirring, swirling the pan occasionally, until deep amber, 8–10 minutes. Off the heat, whisk in the butter (it will foam), then pour in the warm cream in a steady stream, whisking. Return to low heat for 1 minute and whisk until smooth.

STEP 8: SEASON THE CARAMEL

Stir in the flaky sea salt. Taste on a cooled spoon: the salt should be distinctly present, not just a background note. Cool to room temperature; the caramel should be thick but still flow off a spoon.

STEP 9: COOK THE BRITTLE SYRUP

Line a rimmed baking sheet with a silicone baking mat. Heat the sugar, light corn syrup and water in a heavy saucepan, stirring until the sugar dissolves, then boil without stirring until it reaches 300°F on a candy thermometer.

STEP 10: FINISH THE BRITTLE

Take the pan off the heat and quickly stir in the butter and vanilla extract, then the roasted peanuts, then the baking soda. The mixture will foam. Pour at once onto the lined sheet and spread thin. Cool completely, then break half into shards for decoration and finely chop the rest.

STEP 11: MAKE THE PEANUT BUTTERCREAM

In a stand mixer, beat the butter and peanut butter together until pale, 3–4 minutes. Add the powdered sugar in three additions on low speed, then the heavy cream, vanilla extract and fine salt. Beat on medium-high until light and fluffy, 3–4 minutes, adding the cream a little at a time until the buttercream pipes easily but holds a firm edge. Spoon into a piping bag.

STEP 12: LAYER THE CAKE

Level the sponges if domed. Set the first sponge on a serving plate, pipe a thick layer of peanut buttercream over it, drizzle with a little salted caramel and scatter with some of the finely chopped brittle. Repeat with the second sponge, then top with the third, base side up.

STEP 13: ADD THE CARAMEL DRIP

Spread a thin layer of buttercream over the top of the cake and chill for 15 minutes to firm. Pour the remaining salted caramel over the top and let it run over the edges in loose, generous drips; do not tidy it into a neat glaze. Finish with the chopped peanuts and stand the brittle shards upright in the top.