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.