When the water in the saucepan starts to simmer, turn the heat down to a gentle simmer and set the bowl with the wet ingredients over it ensuring that the water doesn't touch the bowl.
Cook, stirring occasionally until the sugar is dissolved, about 10 min. Now add 2 eggs and continue to whisk constantly until well mixed in. Next add the 1 tsp of baking soda and cook for about 10 minutes whisking constantly.
Combine the dry & the wet: Pour the wet (hot) ingredients into the dry ingredients and mix until everything is combined. (Do not discard the saucepot with water, we'll use the water bath later in the recipe).
The dough will be very sticky, but will become not sticky as it cools. Divide the dough into 8 and keep covered the pieces you're not working with.
Preheat the oven to 375F degrees as you roll the cake layers.
Roll each chocolate dough piece between two layers of parchment paper to a slightly larger than an 8 inch circle. Poke with a fork about every 1 inch and bake for about 5-7 minutes. Do not let the edges burn or brown. Remove from the oven and place an 8-inch round template (plate or an 8-inch round baking pan) and cut around it, removing the scraps to a bowl.
Repeat with the remaining dough.
Crush the crumbs: Once all the scraps are cool, crumble them into a fine crumbs by pulsing them in a blender, crushing them between your hands, or by adding into a ziplock bag and rolling with a rolling pin.
Whip Butter: In a separate bowl whip room temperature butter for about 5-7 minutes or until it is pale in color and fluffy, stopping several times to scrape down the sides and bottom. Set aside.
Sour cream custard: In a heatproof bowl combine 3/4 cups sugar, 2 tbsp cornstarch and 2 eggs, then add 1 tsp vanilla, 2 cups sour cream, set over the sauce pot with simmering water and stir until smooth. Cook until the cream is thickened or until it's about 175F°, about 20 minutes. The cream will start out thick, then thin down as it heats and thicken back up again when the cornstarch and the eggs thicken it again.
Allow to cool completely (to room temperature, not colder). You can place the bowl into iced water to quicken the process.
Combine: Add the cooled sour cream custard into the whipped butter in fourths, whipping well after each addition.
Combine 2 tbsp boiling hot heavy cream with 2 tbsp dark chocolate chips and allow to sit for 1 minute. Stir until smooth.
Place a dab of cream in the middle of the serving platter or a cake board. Top with the chocolate cake layer and press to adhere. Now layer the cake with 2 scoops of cream between each layer, covering the outside with cream as well.
Pour the ganache over the top of the cake and even it out over the top.
Press the crushed cake crumbs against the sides of the cake, going slightly over the edge of the top creating a border with crumbs.
Refrigerate overnight before serving.
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