Pre-heat an oven to 350f. Cream the unsalted butter, until creamy and pale.
Add the caster sugar and vanilla extract. Mix well.
In a separate bowl, sift the flour, baking powder and salt.
Add the eggs, one at a time to the butter mixture. Mix until combined.
Add one-third of the flour mixture to the egg and butter mixture. Combine well.
Add half of the heavy cream to the batter and combine.
Continue adding the flour mixture and heavy cream to the batter until fully combined.
Divide the butter in half in two separate bowls.
Add to one of the batters the cocoa powder and mix well.
Pour into a loaf pan the vanilla and cocoa batters by placing scoops of them, simulating a chess board.
Using a toothpick or a point sharp knife, mix gently, both batters, performing a wave-like shape.
Transfer to a pre-heated 350f oven and bake for 35’