Preheat the oven to 180°C and line two, 20 cm round baking pans with parchment paper (grease and flour the pan with butter and breadcrumbs). I used the disposable aluminum type that can be found at the supermarket, without any issues.
In a large bowl (even that of a stand mixer, if you have one) mix the eggs, buttermilk, yogurt, oil, and vanilla; add the sugar, then the flour, cocoa, baking powder, and baking soda together, little by little, working the batter with the electric whisks.
Add the water or coffee and mix slowly until the water has been well absorbed and incorporated into the batter, which must remain liquid enough to be poured into the cake pans without effort.
Divide the batter into the two previously prepared cake pans and cook the cakes for 20-25 minutes until they appear cooked well, even in the middle.
Remove the cakes from the oven, and let them cool for a few minutes, then turn them on a plate to remove them from the baking pans.
Allow the two cake bases to cool completely, or even better, place them in the freezer for half an hour before assembling the complete dessert with mascarpone cream