Prep Time: 40 minutes (includes frosting)

Cook Time: 35-40 minutes

Cooling/Assembly Time: 2 hours

Total Time: 3 hours 20 minutes

Serves: 12-16

Difficulty: Intermediate

Intensity: Moderate (requires careful mixing and a two-step frosting process)

Ingredients

For the fudgy Chocolate Cake:

2 cups (400g) granulated sugar

1 ¾ cups (220g) all-purpose flour

¾ cup (75g) Dutch-processed cocoa powder, plus extra for dusting pans

2 tsp baking soda

1 tsp baking powder

1 tsp fine sea salt

2 large eggs, at room temperature

1 cup (240g) full-fat mayonnaise (see The Mayonnaise Miracle note)

1 tbsp pure vanilla extract

1 cup (240ml) hot, strongly brewed coffee (or boiling water)

4 oz (115g) high-quality semi-sweet or bittersweet chocolate, finely chopped

½ cup (120ml) buttermilk, at room temperature

For the Satin Fudge Frosting:

1 ½ cups (340g) unsalted butter, softened but cool, divided

4 oz (115g) unsweetened chocolate, chopped

1 cup (85g) Dutch-processed cocoa powder, sifted

5 cups (600g) powdered sugar, sifted

½ cup (120ml) whole milk or heavy cream, at room temperature

2 tsp pure vanilla extract

¼ tsp fine sea salt

For Simple Assembly & Garnish:

Chocolate shavings or sprinkles

Flaky sea salt (optional, for a gourmet touch)

Instructions

The Pudgy Cake Layers (The Moisture Magic)

Prep & Preheat: Preheat oven to 350°F (175°C). Grease two 9-inch round cake pans. Line the bottoms with parchment paper rounds, then grease the parchment. Dust the entire inside of each pan with cocoa powder, tapping out excess. This prevents sticking and avoids a white flour residue.

Whisk Dry Ingredients: In a large bowl, sift together the flour, ¾ cup cocoa powder, baking soda, baking powder, and salt. Whisk for a full minute to aerate and combine thoroughly.

Melt Chocolate: Place the 4 oz of chopped semi-sweet chocolate in a heatproof bowl. Pour the hot coffee over it. Let sit for 2 minutes, then whisk until the chocolate is completely melted and the mixture is smooth. Set aside to cool slightly.

Combine Wet Ingredients: In the bowl of a stand mixer fitted with the paddle attachment, combine the sugar, eggs, mayonnaise, and vanilla. Mix on medium speed for 2-3 minutes until the mixture is pale, smooth, and emulsified. The mayonnaise should be fully incorporated with no visible traces.

The Critical Alternating Add: With the mixer on low speed, add one-third of the dry ingredients, mixing until just combined. Follow with half of the buttermilk. Repeat with another third of dry ingredients, the remaining buttermilk, and finally the last of the dry ingredients. Mix only until each addition is incorporated; do not overmix.

Incorporate Chocolate-Coffee: Finally, with the mixer still on low, slowly pour in the slightly cooled chocolate-coffee mixture. Mix until the batter is uniform—it will be very thin, almost like a thick chocolate soup. This is correct.

Bake: Divide the batter evenly between the prepared pans. Bake for 30-38 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs attached (not wet batter). The tops will be domed and spring back lightly.

Cool Completely: Let cakes cool in pans on a wire rack for 20 minutes. Then, run a thin knife around the edges, invert onto the rack, and peel off the parchment. Allow to cool completely before frosting. Pro-Tip: Wrap cooled layers tightly in plastic wrap and freeze for 1 hour. This makes them easier to frost and locks in moisture.

The Satin Fudge Frosting (The Glossy Crown)

Melt Chocolate & Butter: In a heatproof bowl set over a pot of simmering water (double boiler), melt the unsweetened chocolate and ½ cup (1 stick) of the butter together, stirring until smooth. Remove from heat and let cool to room temperature.

Cream Base: In a stand mixer fitted with the paddle attachment, beat the remaining 1 cup (2 sticks) of softened butter on medium-high speed for 5 minutes, until very pale and fluffy.

Build the Frosting: Reduce speed to low. Gradually add the sifted powdered sugar and cocoa powder, alternating with the milk/cream, beginning and ending with the dry ingredients. Scrape down the bowl as needed.

Incorporate Melted Chocolate: With the mixer on low, pour in the cooled, melted chocolate-butter mixture, vanilla, and salt. Increase speed to medium-high and beat for 3-4 minutes, until the frosting is incredibly light, fluffy, and has a satiny sheen. It should hold a firm peak.

Assembly – Keep it Simple & Classic

Level (Optional): If your cake layers have a significant dome, use a serrated knife to carefully slice off the top to create a flat surface.

Stack & Frost: Place one cake layer on a serving plate or cake stand. Spread a generous, even layer of frosting (about 1 cup) over the top. Carefully place the second layer on top.

Crumb Coat: Apply a thin layer of frosting over the entire cake to seal in crumbs. Refrigerate for 20 minutes to set.

Final Frosting: Use the remaining frosting to create a beautiful, thick final coat. For a classic look, use an offset spatula to create smooth sides and a swirled top. For a more rustic, “pudgy” look, use a spoon to create intentional, soft peaks.

Garnish: Immediately garnish the top with chocolate shavings or a light sprinkle of flaky sea salt.

 The All-Important Slice

Serve: For the cleanest slice and best texture, let the cake sit at room temperature for at least 30 minutes after assembly. Use a sharp knife dipped in hot water and wiped dry between cuts.

The Baker’s Almanac: Why This Cake Works

The Mayonnaise Miracle: Do not flinch. Mayonnaise is simply eggs and oil—two foundational cake ingredients. Here, it replaces the usual butter/oil and adds extra emulsifiers, guaranteeing an unbelievably moist, tender, and even crumb with zero “mayo” flavor.

Double Chocolate Dose: Using both cocoa powder (for deep flavor) and melted bar chocolate (for richness and smooth mouthfeel) creates a complex, multi-layered chocolate experience that powder alone cannot achieve.

Hot Coffee is Key: The hot liquid blooms the cocoa powder, intensifying its flavor, and helps melt the chocolate seamlessly into the batter. It also encourages the formation of a tender crumb.

The Frosting Philosophy: This frosting is a hybrid—creamy like a German buttercream but with the intense fudge flavor of an American style. Melting a portion of the butter with unsweetened chocolate ensures a smooth, non-grainy texture and a profound chocolate base.

Storage & Make-Ahead:

Cake Layers: Can be baked, wrapped tightly, and frozen for up to 2 months. Thaw in the refrigerator before frosting.

Frosting: Can be made up to 3 days ahead, stored in an airtight container in the fridge. Re-whip at room temperature before using.

Full Cake: Once frosted, the cake can be kept, covered, at cool room temperature for 1 day or refrigerated for up to 4 days. Always bring to room temperature before serving.

Nutritional Information (Per serving, 1/16th of cake, approximate):

Calories: ~720 kcal

Total Fat: 39g

Saturated Fat: 20g

Cholesterol: 85mg

Sodium: 420mg

Total Carbohydrates: 92g

Dietary Fiber: 4g

Sugars: 74g

Protein: 6g