Portuguese Coffee Buttercake

This is a patience project in the best sense. Twelve paper-thin butter wafers baked separately on the backs of inverted cake pans, then stacked with layers of coffee-flavored French buttercream between each one. The result is a striped cake with 24 visible layers when sliced.

The wafer technique is the hallmark. Baking each wafer on the bottom of an inverted pan gives you a flat, even disc with no risen edges or domed middle. Each one goes in the oven for 10 to 12 minutes only, so you’ll spend an hour cycling batches. It’s tedious but unavoidable.

French buttercream is the rich kind, made with egg yolks instead of whites. Hot milk cooks the yolks and sugar into a custard base, then cool butter gets beaten in one tablespoon at a time. The instant coffee is added warm, so it dissolves fully. The finished buttercream is silkier and more indulgent than Swiss meringue or American-style.

Pro Tips

• Butter the inverted pans lightly but thoroughly, then flour. Any missed spot and the wafer sticks, tearing as you try to lift it.
• Spread the batter right to within a quarter inch of the edge. Thinner layers closer to the edge bake up evenly.
• Let each wafer cool fully flat before stacking. Warm wafers bend and the stack ends up crooked.
• Add the butter to the custard base one tablespoon at a time, waiting for each addition to incorporate before the next. Fast addition means broken buttercream that looks curdled.

Variations

• Swap instant coffee for a tablespoon of cocoa powder and a teaspoon of espresso powder for a mocha buttercake.
• Stir a tablespoon of dark rum or cognac into the cooled custard base for a boozy grown-up version.
• Garnish the top with chocolate-covered coffee beans for a visual and flavor cue.