Step 1

You can use traditional or nonalcoholic porter beer in this recipe. Plan ahead: The currants and raisns need to soak for at least 8 hours before proceeding with the recipe. We call for both dark and golden raisins here for a greater depth of flavor, but you can use a single variety if you prefer. Do not substitute liquid buttermilk for the buttermilk powder; the buttermilk powder in the frosting reinforces the tangy flavor of the cream cheese without making the frosting too soft. To ensure the proper spreading consistency for the frosting, use cold cream cheese and butter that's softened but still somewhat firm (about 65 degrees).

Step 2

FOR THE CAKE: Combine porter, raisins, golden raisins, and currants in bowl. Cover and let sit until fruit is plump, at least 8 hours or up to 24 hours. Drain fruit in fine-mesh strainer set over bowl, gently tossing fruit to release liquid; reserve fruit and ⅔ cup porter and discard any extra porter.

Step 3

Adjust oven rack to middle position and heat oven to 350 degrees. Grease three 8-inch round cake pans, line with parchment paper, and grease parchment. Whisk flour, baking powder, baking soda, ginger, nutmeg, and salt together in bowl.

Step 4

Whisk 1¼ cups sugar, oil, eggs, vanilla, and lemon zest in separate bowl until smooth. Stir in drained fruit. Fold in flour mixture until just combined. Divide batter evenly among prepared pans and smooth tops with silicone spatula. Bake until cakes are set and skewer inserted in centers comes out clean, 25 to 28 minutes. Let cakes cool in pans on wire racks for 5 minutes. Invert cakes onto racks, discarding parchment. Using skewer, poke 30 holes in each cake layer.

Step 5

Bring reserved ⅔ cup porter and remaining ⅔ cup sugar to simmer in large saucepan over high heat. Reduce heat to medium-low and simmer until syrup is thick, frothy, and reduced to ⅔ cup, 5 to 10 minutes, adjusting heat as needed to maintain active simmer without allowing syrup to froth over. Off heat, once frothing subsides, measure out ¼ cup syrup and brush over warm cakes. Let cakes cool completely on racks, about 2 hours.

Step 6

Meanwhile, return remaining syrup to simmer over medium-low heat. Off heat, whisk in chilled butter until smooth. Transfer syrup to bowl and set aside to cool completely.

Step 7

FOR THE FROSTING: Using stand mixer fitted with paddle, beat butter, sugar, buttermilk powder, vanilla, and salt on low speed until smooth, 2 to 3 minutes, scraping down bowl as needed. Increase speed to medium-low; add cream cheese, 1 piece at a time; and mix until smooth, 2 to 4 minutes.

Step 8

Place 1 cake layer on cake platter, syrup side up. Spread 1 cup frosting evenly over top, to edges of cake. Repeat with remaining layers, spreading 1 cup frosting evenly over each. Spread thin layer of frosting evenly over sides of cake, scraping sides with edge of offset spatula to create sheer veil of frosting. (Cake sides should still be visible.) Transfer remaining frosting to pastry bag fitted with large (½- to ¾-inch) tip. Pipe frosting in 1-inch mounds in ring around perimeter of cake top, leaving ¼-inch border around edge. Refrigerate cake until frosting is set, at least 1 hour.

Step 9

Stir cooled porter syrup to loosen, then drizzle 2 tablespoons porter syrup around edge of cake, allowing it to drip down sides. (Microwave syrup as needed, for a few seconds at a time, if it is too thick to drizzle.) Serve cake with any remaining porter syrup or reserve syrup for another use. (Cake can be refrigerated for up to 24 hours.)