Malted chocolate marble cake

Preheat the oven to 180°C, gas mark 4. Grease and line a 900g loaf tin with baking parchment. In a small pan, melt the butter over a medium-high heat, swirling the pan occasionally, until it starts to turn golden and smells nutty. Pour into a bowl and set aside to cool for 20 minutes.

Meanwhile, tip the flour into a large frying pan and toast, stirring regularly for 8-10 minutes, until light golden brown. Sieve into a large mixing bowl. Add the sugar, baking powder and salt, then whisk to mix. Make a well in the centre, then add the eggs and cooled butter. Mix to a smooth batter, then fold in the soured cream. Bring a kettle to the boil.

Put the Ovaltine and cocoa into a small bowl and add 3 tbsp just-boiled water; stir until smooth. Spoon 200g of the batter into another bowl and fold in the cocoa mixture until just combined. Alternatively spoon the plain and cocoa batters into the tin, then lightly ripple them together with a skewer. Bake for 40-50 minutes, or until a skewer inserted into the centre comes out clean. Let cool completely in the tin.

Once the cake is cool, preheat the grill to medium-high. Remove the cake from the tin and transfer to a baking sheet. Chop the marshmallows and arrange on top, sticky-side-down. Grill for 1-2 minutes, or until the marshmallows are golden; leave to set for 2 minutes before serving.