Martha's Carrot cake traybake

Preheat the oven to 170°C, gas mark 3. Line a 23cm x 33cm tray with baking parchment.

In a large bowl, whisk the sugars, oil and eggs together until smooth. Slowly add the flour, bicarbonate of soda, baking powder, cinnamon, ginger and salt, and continue to beat until well mixed.

Stir in the grated carrots and chopped walnuts until they are evenly dispersed. Pour into the lined tin and bake for 35-40 minutes or until golden brown and a skewer inserted comes out clean. Allow to cool in the tin for 20 minutes, then cool fully on a wire rack before icing.

To make the icing, use an electric whisk to blend the cream cheese and butter together. Add the icing sugar in a few separate additions until it is all combined, then whisk on high speed for 5 minutes until the mixture is thick, pale and light.

For the brittle, arrange the walnuts on a baking tray lined with baking parchment and place the caster sugar in a saucepan with 2 tbsp of water. Simmer over a medium heat until the sugar has dissolved, then turn the heat up and boil until it turns a dark amber colour. Carefully pour the hot caramel over the nuts and leave to cool completely before breaking up and blitzing in a food processor to create chunks of brittle.

Spread the icing over the cooled cake and sprinkle the brittle over the top before slicing into squares.