Rum-Scented Marble Cake

Ingredients

• Base Batter:
• 2 2/3 cups all purpose flour
• 1 2/3 cups sugar
• 2 teaspoons baking powder
• 1/4 teaspoon salt
• 12 ounces unsalted butter, softened
• 7 large eggs
• 3 tablespoons dark rum
• Chocolate Batter:
• 2 tablespoons dark rum
• 2 tablespoons milk
• 1/2 teaspoon baking soda
• 6 ounces bittersweet chocolate, melted and cooled
• 2 cups Base Batter, above

Directions

1. Move an oven rack to the lower third, then heat the oven to 325 degrees F. Put the flour, sugar, baking powder, and salt into the bowl of an electric mixer, stir them together by hand, and add the butter. Using the paddle on low speed, mix until it turns into a thick, smooth paste, about a minute or two.
2. Whisk the eggs with the rum. Set the mixer to medium speed and blend a third of that liquid into the flour-butter mixture. Keep beating for 1 minute. Pause and scrape down the bowl and the beater. Mix in another third of the liquid, then continue for 2 minutes. Add the final third and beat for 2 minutes as well. Take the bowl off the mixer and give the batter a last thorough stir with a large rubber spatula.
3. In a medium mixing bowl, put the rum, milk, and baking soda, and whisk until the soda dissolves. Add the chocolate and whisk it smoothly into the rum mixture. Whisk in the 2 cups of base batter until the chocolate mixture is even.
4. Scoop half of the base batter that remains into the prepared pan, and level it. Spread the chocolate batter over it, aiming for an even layer. Finish with the rest of the base batter, smoothing that surface too.
5. For marbling, choose either a table knife with a wide blade or a thin metal spatula. Slide the blade into the batter beside the central tube, with the broad side turned toward you. Pull it down through the batter to the bottom of the pan, then bring it up along the side nearest you and out. Repeat that motion about every inch as you work around the pan, so the path spirals through the batter, a little like folding in egg whites. When you return to your starting place, stop. Resist neatening the top afterward, since that can smear the marbling.
6. Bake until the cake rises high and feels firm; test it halfway between the pan wall and the central tube with a toothpick or a small, thin knife, which should come out dry, about an hour. Let the cake rest in the pan for 5 minutes, then set a rack over it. Turn the cake over and remove the pan. Leave the cake to cool completely. When cool, cover the cake with plastic wrap; it can stay at room temperature. For longer storage, freeze it. Defrost and bring the cake to room temperature before you serve it.