The moment it comes out of the oven, this giant slab of chocolate cake is doused in hot fudge and buried under an avalanche of crunchy pecans. The soft, warm cake soaks up the molten fudge, a combination that creates a delightfully gooey layer sandwiched between the fluffy cake below and the fudgy frosting on top. It's big enough to feed a crowd, but it keeps so well that a small family could nibble on it for a week, making it the sort of recipe every baker should have in their repertoire.
For best results, avoid low-fat supermarket cocoa powder (which is, conversely, high in starch), and look for brands that don't skimp on the cocoa butter; read up on our recommended natural cocoa powders for more information.
Why It Works
- High-fat natural cocoa is relatively low in starch, for a full-flavored cake that's rich, moist, and aromatic, never crumbly or dry.
- Natural cocoa powder is slightly acidic, which helps to fuel the baking soda for the cake's rise.
- Malted milk powder adds notes of toffee and malt for complexity, deepening the flavor of the cake.
- Boiling the glaze to 220°F (104°C) brings out the cocoa's full flavor and ensures consistent results time after time.
- Yield:25 roughly 2 1/2–inch pieces
- Active time: 1 hour
- Total time:1 hour
- For the Cake:
- 12 ounces light brown sugar (about 1 1/2 cups, packed; 340g)
- 10 ounces unsalted butter (about 20 tablespoons; 280g), soft but cool, about 65°F/18°C, plus more for greasing the pan
- 1 3/4 teaspoons baking soda
- 1 teaspoon (4g) Diamond Crystal kosher salt; for table salt, use about half as much by volume or the same weight
- 1/4 teaspoon ground cinnamon
- 1/2 ounce vanilla extract (about 1 tablespoon; 15g)
- 4 large eggs (about 7 ounces; 200g), brought to about 70°F/21°C
- 10 ounces all-purpose flour, such as Gold Medal (about 2 1/4 cups, spooned; 280g)
- 2 ounces natural cocoa powder, not low-fat (about 2/3 cup, spooned; 55g), plus more for dusting (see note)
- 1 ounce malted milk powder, such as Carnation (1/4 cup; 30g); optional
- 12 ounces cultured low-fat buttermilk or kefir (about 1 1/2 cups; 340g), brought to about 70°F/21°C , or a 50/50 blend of milk and plain yogurt
- For the Chocolate Glaze:
- 8 ounces milk, any percentage will do (about 1 cup; 225g)
- 6 ounces unsalted butter (about 12 tablespoons; 170g)
- 7 ounces sugar (about 1 cup; 200g)
- 1 1/2 ounces natural cocoa powder, not low-fat (about 1/2 cup, spooned; 40g)
- 1/4 teaspoon (1g) Diamond Crystal kosher salt, or more to taste; for table salt, use about half as much by volume or the same weight
- 1/4 teaspoon vanilla extract
- 8 ounces toasted pecan halves (about 1 1/2 cups; 225g), or to taste, lightly crumbled or chopped
For the Cake: Adjust oven rack to lower-middle position and preheat to 350°F (180°C). Grease a half-sheet pan, dust with cocoa, and tap out the excess.
Combine brown sugar, butter, baking soda, salt, cinnamon, and vanilla extract in the bowl of a stand mixer fitted with a paddle attachment. Mix on low to moisten, then increase to medium and cream until fluffy and light, pausing to scrape the bowl and beater halfway through, about 5 minutes. With the mixer running, add the eggs one at a time, letting each fully incorporate before adding the next and scraping the bowl as needed.
Meanwhile, sift together the flour, cocoa, and malted milk powder (if using). Reduce mixer speed to low and sprinkle in a third of the dry mix, followed by a third of the buttermilk. Alternate between the two, allowing each addition to roughly incorporate before adding the next. Once batter is smooth, fold with a flexible spatula to ensure it’s well mixed from the bottom up. Scrape batter into the prepared pan, then spread into an even layer.
Bake until the cake is puffed and firm to the touch, though your finger will leave an indentation in the puffy crust, about 25 minutes.
Meanwhile, for the Chocolate Glaze: While the cake is baking, combine the milk, butter, sugar, cocoa powder, and salt in a 2-quart stainless steel saucier. Warm over medium-low heat until the butter is melted, then increase heat to medium and bring to a boil, whisking from time to time, until the mixture is homogeneous. Continue cooking until the syrup reaches 220°F (104°C), then shut off the heat and stir in the vanilla. Cover and set aside to keep warm until the cake comes out of the oven.
As soon as the cake is done, immediately pour the warm glaze on top, working slowly to prevent overflow and using an offset spatula or the back of a spoon to smooth it into an even layer. Cover all over with toasted pecans, as few or as many as you like. Enjoy warm, or let it stand at room temperature until the glaze has fully set. Wrapped in plastic, the glazed cake will keep up to 1 week at room temperature.