1. Preheat oven to 350F. Line a 9-inch cake pan with a circle of parchment paper on the bottom. Spray the sides of the pan with nonstick spray.

2. In a large bowl, add cocoa powders and hot water, or hot coffee. Whisk to combine. Add in butter sugar, yogurt (or sour cream), egg and vanilla extract. Whisk to combine. Add in sifted flour, baking soda, baking powder and salt. Mix just until combined.

3. Pour batter into prepared cake pan and bake 18-22 minutes, or until a toothpick inserted into the center comes out clean.

4. Make the chocolate mousse. In a medium size bowl, whisk together egg yolks and sugar. In a medium size saucepan, add heavy cream and heat over medium-low heat until it simmers. Pour warm cream over egg yolks, while whisking egg yolks constantly. Pour the egg yolk mixture through a fine mesh sieve back into the saucepan (this is to catch any egg yolks that may have scrambled). Cook, stirring constantly over medium-low heat until mixture is thickened. Turn off heat and add in chocolate chips. Stir until melted.

Pour the mixture into a bowl and cover with plastic wrap. Cool in refrigerator for 1-2 hours, or until completely cooled.

5. Once the cake is completely cooled, and the chocolate mixture for the chocolate mousse is cooled, get ready to finish making the mousse and assemble.

Finish the mousse. In the bowl of a stand mixer fitted with the whisk attachment, or using a large bowl and handheld mixer, whip heavy cream and powdered sugar until very stiff peaks are formed. Add whipped cream into the chocolate mixture and fold until completely combined.

Place the chocolate cake in a 9-inch springform pan with a piece of parchment paper lining the pan.

Add the chocolate mousse on top of the cake and spread into an even layer.

6. Make the chocolate ganache. In a medium size saucepan, bring heavy cream to a simmer, remove from the heat and add in the chocolate chips. Stir until melted. Alternatively, add heavy cream to a microwave safe bowl and microwave in 30 second increments until it reaches roughly 180F. Pour the heavy cream over the chocolate chips and stir until the chocolate chips are melted.

Pour the chocolate ganache over top of the mousse.

7. Place cake in refrigerator and allow to chill in the refrigerator for 4-6 hours, or overnight.