It's probably a bit late to make this cake for this weekend but maybe next weekend?
It's a riff on this one. The body of the cake is the same but the swirly bit is slightly different.
Hazelnut Mocha Swirl Cake
You need a greased tray-bake tin 9" x 13"
In a bowl put
500g (1lb 2oz) plain flour
½ teaspoon salt
210g (7½oz) caster sugar
4 teaspoons baking powder
340ml (12 fl oz) milk
Mix well, then add gradually, mixing as you go
112g (4oz) melted butter
Pour the batter into the tin.
Next make the hazelnut mocha filling.
Mix together well
227g (8oz) soft butter
190g (7oz) dark soft brown sugar
1 tablespoon flour
½ tablespoon instant coffee powder I used Carte Noire Expresso powder
1½ tablespoons cocoa powder
85g (3oz) plain chocolate chips
85g (3oz) chopped hazelnuts
Dollop spoonfuls of the filling on top of the cake batter. Then use a knife to swirl it through the cake.
Bake the cake at 180°c (160°c fan oven) for 40mins
Optional: while the cake is still warm pour over an icing made by mixing about 2 tablespoons of icing sugar, 1 teaspoon of instant espresso powder and enough water or milk to make a runny mixture.