For the Chocolate Cake
1-Preheat oven to 350°F: Preheat oven to 350°F.
2-Grease or spray (3) 9” round cake: Grease or spray (3) 9” round cake pans. Line the bottom of each pan with parchment paper.
3-Using a medium mixing bowl, whisk together: Using a medium mixing bowl, whisk together cocoa powder and boiling water until smooth; set aside.
4-Using a large bowl, add the dry: Using a large bowl, add the dry ingredients (flour, sugar, brown sugar, baking powder, baking soda and salt); whisk until well combined.
5-Add eggs, egg yolks, vegetable oil, sour: Add eggs, egg yolks, vegetable oil, sour cream and vanilla; whisk until well combined.
6-Finally, add the cocoa powder and hot: Finally, add the cocoa powder and hot water mixture to the bowl in several additions, whisking well between each addition.
7-Divide batter evenly into baking pans: Divide batter evenly into baking pans; tap pans lightly on countertop to release any air bubbles.
8-Bake at 350°F for 25-27 minutes, or: Bake at 350°F for 25-27 minutes, or until a toothpick inserted into center of cake comes out clean.
9-Let cakes cool in pan for 15: Let cakes cool in pan for 15 minutes and then transfer cake layers to a wire rack until completely cool. (Note: Remove parchment paper from bottom of cakes when transferring them to the racks.)

For the Chocolate Ganache
10-Using a microwave-safe bowl, add the chopped: Using a microwave-safe bowl, add the chopped chocolate and heavy cream. Microwave in 30 second intervals, stirring after each interval, until chocolate has fully melted and mixture is smooth.
11-Let ganache stand for 10 minutes to: Let ganache stand for 10 minutes to thicken slightly.

For the Salted Peanut Caramel Sauce
12-Using a medium saucepan, add sugar and: Using a medium saucepan, add sugar and water; stir until well combined. (Note: Use a larger saucepan than you think as the mixture will expand rapidly when the cream is added later.)
13-Place over medium-high heat and cook, stirring: Place over medium-high heat and cook, stirring often, for about 10 minutes, or until mixture is amber colored.
14-Remove from heat and add heavy cream: Remove from heat and add heavy cream; stir until well combined. (Note: The mixture will bubble up rapidly when the cream is added, so be careful!)
15-Add salt, vanilla and chopped peanuts: Add salt, vanilla and chopped peanuts; stir until well combined.
16-Immediately assemble cake before the sauce hardens: Immediately assemble cake before the sauce hardens. (Note: If sauce begins to thicken too much to spread, just put the saucepan back over medium heat until it loosens up. You can also add a splash of additional cream if needed.)

To Assemble
17-Place one layer of cake on large: Place one layer of cake on large serving plate.
18-Pour ¼ of the chocolate ganache on: Pour ¼ of the chocolate ganache on top of the cake; use an offset spatula to spread ganache to the edges of the cake.
19-Spread ¼ of the caramel sauce on: Spread ¼ of the caramel sauce on top of the chocolate ganache.
20-Repeat process with another layer of cake: Repeat process with another layer of cake and another ¼ of the ganache and caramel sauce.
21-Place 3rd layer on top of cake: Place 3rd layer on top of cake.
22-Spread the remaining ½ of chocolate ganache: Spread the remaining ½ of chocolate ganache on top.
23-Spread the remaining ½ of the caramel: Spread the remaining ½ of the caramel sauce on top, letting the excess drip down the sides of the cake.