Preheat your oven to 350°F. Prepare a 9-by-9-inch square baking pan by lining it with aluminum foil, allowing some overhang for easy removal. Lightly spray the foil with cooking spray to prevent sticking.
In a large mixing bowl, combine the large egg, granulated sugar, Greek yogurt, and canola oil. Whisk these together until the mixture is smooth and well-combined, creating a creamy base.
Next, incorporate the strongly brewed coffee and unsweetened cocoa powder into the batter. Whisk vigorously to ensure a smooth consistency without lumps. The coffee will amplify the chocolate flavor, making it rich and deep.
Add the all-purpose flour, baking soda, baking powder, and salt to the mixture. Stir gently until just combined, being careful not to overmix; this will help keep the cake tender.
Pour the batter into the prepared pan. Use a spatula to smooth the top lightly, ensuring an even baking surface.
Bake in the preheated oven for about 25 to 29 minutes. You’ll know it’s done when the top is set and a toothpick inserted in the center comes out clean. Baking times may vary, so keep an eye on your cake!
Allow the cake to cool completely in the pan on a wire rack. This cooling step is crucial for achieving the right texture.
Once cooled, lift the cake out of the pan using the foil overhang. Place it on a cutting board and use a 3 to 4-inch diameter cookie cutter to cut out rounds. Enjoy nibbling on the edges and scraps!
For the hot fudge, either prepare your own using a trusted recipe or opt for a thick store-bought version. Avoid thin sauces, as they won’t hold up well on the cake.
Assemble your cake layers shortly before serving. Place a cake round on a serving platter, top with about 3 tablespoons of hot fudge, and spread it evenly. Repeat this layering until all rounds are stacked. Finish with sprinkles if desired, and enjoy the delicious chaos that follows!