In a bowl, whisk together eggs, oil, buttermilk, Nutella & cold coffee until combined. Sieve in the flour, bicarbonate of soda, cocoa powder and salt. Using a spatula mix it well. Grease and line 2 6” cake tin. Pour the batter and bake it at 170 C for 20-25mins
Now, using a stand or hand mixer whip the butter for 5mins until pale, light & fluffy. Add icing sugar and whisk for 2mins. Add the Nutella and double cream and whisk till it’s smooth.
Heat the cream on medium to low heat. Add the heated cream onto butter and chocolate and Nutella and whisk well. Set it aside for it to cool and firm a bit.
Assemble the cake by layering it with cooled ganache and cover it light sort of a crumb coat. I have gone for a semi-naked cake look. Top it with buttercream swirls.