Step: 1/12

Preheat the oven to 180°C (160°C fan, gas 4). Grease a ring cake tin with butter and sprinkle with crumbs.

Step: 2/12

Whisk the butter until soft and creamy.

Step: 3/12

Whisk in the sugar until creamy.

Step: 4/12

Add the vanilla sugar and salt.

Step: 5/12

Grate the zest from the lemon and beat into the batter.

Step: 6/12

Gradually add the eggs, whisking constantly.

Step: 7/12

Add some milk.

Step: 8/12

Sieve the flour with the baking powder and starch and add to the batter, alternating with the milk until a soft dropping consistency is formed.

Step: 9/12

Spoon half the mixture into the prepared tin.

Step: 10/12

Mix the cocoa powder into the other half. Add a little milk if necessary.

Step: 11/12

Spread the chocolate mix evenly over the plain mix and pull a fork randomly to swirl the mixtures together.

Step: 12/12

Bake in the preheated oven for about 1 hour. Test with a skewer. Remove from the oven, allow to cool slightly, turn out of the tin and cool completely. Sprinkle with icing sugar and serve in slices.