Mocha Walnut Cake

Traybakes are a great way to create plentiful portions of cake with minimum fuss.

Cut it into generous cake bars for 14, or into squares for smaller tasty treats!

Ingredients (Serves 14):


  • 70g good quality cocoa powder (we use Green & Black’s)
  • 1 heaped teaspoon instant coffee
  • 1 rounded teaspoon bicarbonate of soda
  • 200ml boiling water
  • 4 large eggs
  • 375g soft brown sugar
  • 180ml rapeseed oil
  • 200g self-raising flour
  • 60g walnuts, chopped (optional)


  • 275g unsalted butter, very soft
  • 200g mascarpone, room temperature
  • 275g icing sugar
  • 3 heaped teaspoons instant coffee, dissolved in 20ml of boiling water


  • 30g dark chocolate (min. 50% cocoa solids)
  • 14 (or 28) walnut halves (optional)


  1. Preheat the oven to 180ºC (160ºC fan).
  2. Grease a 30cm x 23cm rectangular baking tin (at least 4cm deep). Whisk the cocoa, coffee and bicarb in the 200ml boiling water until combined, then set aside.
  3. In a large bowl, beat together the eggs, sugar and oil until well combined – about 3 minutes. Add the cocoa mixture and stir until incorporated.
  4. Fold in the self-raising flour, and then the walnuts, if using. Pour into the cake tin and bake for 30 to 40 minutes until risen and springy to the touch.
  5. Remove from the oven, run a knife around the edge and leave to cool in the tin.
  6. To make chocolate bark (optional), melt the chocolate in a microwave/over boiling water, then pour onto a cold flat surface – a granite counter is ideal.
  7. Spread to about 3mm thick and leave to set. Once hard, draw a knife blade held in both hands across the chocolate, so that pieces roll or lift up.
  8. For the frosting, beat together the butter and mascarpone until light and fluffy.
  9. Add the icing sugar in three batches, then whisk for about five minutes on high speed.
  10. Pour in the coffee mix and whisk through. Turn the cake out, trim the edges if you want perfectly regular slices, then spread on the frosting.
  11. Decorate with walnut halves and chocolate bark, if using.

Keep the cake in an airtight tin in the fridge (because of the mascarpone) and eat within four days.

The Pennoyer Centre’s staff and volunteer BakeForce make delicious cakes for the café, which won the EDP Norfolk Food & Drink “Best Baking” Award. Please check Pennoyer’s website or Facebook for current opening times. 01379 676660

The Pennoyer Centre, Station Road, Pulham St Mary, Norfolk, IP21 4QT.

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