Old-Fashioned Marble Cake

Ingredients

• ¼ cup (60 ml) water
• ⅓ cup (28 g) unsweetened cocoa powder, preferably Dutch-processed
• 1½ cups (300 g) granulated sugar, divided
• 2 oz (28 g) semisweet or bittersweet chocolate, finely chopped
• 2 cups (278 g) all-purpose flour
• 2 teaspoons baking powder
• ½ teaspoon fine sea salt
• 16 tablespoons (226 g) unsalted butter, at room temperature
• 4 large eggs, at room temperature
• 2 teaspoons pure vanilla extract
• ½ cup (120 ml) full-fat sour cream, at room temperature

Instructions

1. Center a rack in the oven and preheat to 325°F (165°C). Coat a 10-cup Bundt pan thoroughly with baker’s spray, or butter and flour it, tapping out the excess.
2. Bring the water to a boil in a small saucepan. Remove from the heat, whisk in the cocoa powder and ¼ cup of the sugar until smooth, then add the chopped chocolate and stir until melted. Set the chocolate mixture aside to cool slightly.
3. Whisk the flour, baking powder, and salt together in a medium bowl.
4. In a stand mixer fitted with the paddle attachment, or with a hand mixer, beat the butter and remaining 1¼ cups sugar on medium speed for 4 to 5 minutes, until pale and fluffy. Scrape the bowl as needed.
5. Add the eggs one at a time, beating for about 1 minute after each addition. Mix in the vanilla. The batter may look slightly curdled; it will smooth out when the dry ingredients are added.
6. On low speed, add the flour mixture in three additions, alternating with the sour cream in two additions. Begin and end with the flour and mix only until each addition disappears. Finish folding gently by hand.
7. Transfer about one-third of the vanilla batter to the bowl with the chocolate mixture and fold until evenly combined.
8. Spoon alternating mounds of vanilla and chocolate batter around the prepared pan, creating two or three irregular layers. Slide a table knife through the batter once or twice in a loose S pattern. Do not over-swirl.
9. Bake for 55 to 65 minutes, until the cake is well risen, a tester inserted into the center comes out clean, and the top springs back lightly.
10. Cool in the pan on a rack for 10 minutes. Run a thin knife around any exposed edges, then invert the cake onto the rack and cool completely before slicing.