Ingredients
Equipment
Method
- Preheat your oven to 325 degrees Fahrenheit. Line an 8x8 inch square baking pan with parchment paper, letting it hang over the edges for easy removal later.
- Carefully separate the four eggs into yolks and whites, keeping them in two different bowls.
- In a large bowl, beat the softened butter with 3/4 cup granulated sugar using an electric mixer until light and fluffy, about 3 minutes.
- Add the four egg yolks one at a time to the butter mixture, beating well after each addition until fully combined and smooth.
- Sift the all-purpose flour and unsweetened cocoa powder together into a small bowl.
- Add the sifted flour and cocoa powder mixture to the wet ingredients along with the vanilla extract and salt. Fold gently with a spatula until just combined, being careful not to overmix.
- Heat the whole milk in the microwave or on the stovetop until warm but not hot, about 110 degrees Fahrenheit.
- Gently stir the warm milk into the batter until combined.
- In a separate bowl, whip the four egg whites with an electric mixer until stiff peaks form, about 4 to 5 minutes.
- Carefully fold the whipped egg whites into the batter in two batches using a spatula, preserving the airiness.
- Pour the batter into the prepared pan and place it in a larger roasting pan.
- Pour hot water into the roasting pan until it reaches halfway up the sides of the baking pan, creating a water bath.
- Bake for 35 to 40 minutes until the top is golden and springs back when lightly touched, but the center still jiggles slightly when shaken.
- Remove the cake from the oven and water bath, then let it cool completely to room temperature on a wire rack, about 1 hour.
Notes
The cake will look underbaked and jiggly when it comes out of the oven, which is correct. Let it cool completely before serving to achieve three distinct layers — fudgy bottom, creamy custard middle, and light sponge top.