Preheat oven to 350 degrees F.
Mix together cake mix, eggs, vegetable oil and sour cream.
In a microwave safe cup, heat milk in microwave for 60 seconds.
Whisk 2 packs of hot cocoa into milk until well combined.
Pour hot cocoa milk into cake mix and mix until blended.
Spray a 9x13 pan with non-stick cooking spray or line with parchment paper.
Pour cake mixture into pan.
Bake for 20-25 minutes or until toothpick inserted in middle of cake comes out clean.
Let cake cool for 15 minutes and then poke holes in cake.
Heat up chocolate sauce according to jar directions and pour into holes in cake. Let cool for another 15 minutes.
For frosting, melt butter in a small saucepan over low heat. Add in milk and 2 packs hot cocoa mix. Remove from heat and stir in powdered sugar. Stir until well blended.
Spread frosting over top of cake.
Top with Reddi-wip®.