Preheat the oven to 350°F. Lightly grease and flour an 8-inch cake pan.
In a small microwave-safe bowl, combine the butter and chocolate chips. Microwave in 30-second increments, stirring in between, until completely melted and smooth. Set aside to cool slightly.
In another small bowl, lightly beat the eggs with a whisk or fork until the yolks and whites are combined. Set aside.
In a large mixing bowl, whisk together the flour, baking powder, salt, granulated sugar, and cocoa powder.
Add the eggs, vanilla extract, melted butter and chocolate chip mixture, and buttermilk to the dry ingredients. Mix with a wooden spoon until almost fully combined.
Add in the hot water and mix with a wooden spoon just until combined. Be careful not to overmix.
Pour the batter into the prepared cake pan and smooth the top with a spatula. Bake for 40-45 minutes, or until a toothpick comes out clean.
Remove the cake from the oven and let it cool in the pan for 10-15 minutes. Then, transfer the cake to a wire cooling rack to finish cooling.
FOR THE GANACHE FROSTING
Place the chocolate chips in a medium bowl. In a small saucepan or in the microwave, heat the cream just until it begins to boil, remove from heat.
Immediately pour the heated cream over the chocolate. Let stand for 2-3 minutes. Whisk until the chocolate fully melts and the consistency is smooth.
Let the ganache cool in the refrigerator for 30-40 minutes, whisking thoroughly every 10-15 minutes until it firms up and has a frosting-like consistency.
FROST & CHILL
Once completely cooled, spread the ganache frosting evenly across the top and sides of the cake. Add any desired decorations.
Although you can serve this cake immediately, we highly recommend chilling it first. This makes it extra fudgy!! Place it in the refrigerator to chill for at least 30 minutes. Then serve and enjoy.
Notes
For a whipped ganache frosting, whip the ganache after chilling for 30-40 min. Whip it with an electric mixer on high speed until soft peaks form.
For best results, chill the cake in the refrigerator for at least 30 minutes before serving for a super fudgy texture!
The eggs and buttermilk should be at room temperature before getting started.
Measure the flour by using a spoon to scoop the flour into a dry measuring cup and level off the excess with a straight edge.
Use super hot (nearly boiling) water.
Mix with a wooden spoon to avoid overmixing.
Grease the pan with butter or shortening. Then, lightly flour it or line the bottom with parchment paper.
Check the cake for doneness with a toothpick before removing it from the oven. Be careful not to overbake.