Step 1

Preheat the oven to 190°C. Grease and line two 20cm round springform cake pans with baking paper. Sift flour into a large bowl with a pinch of salt. Set aside.

Step 2

Place chocolate in a heatproof bowl, set over a pan of simmering water (don’t let the bowl touch the water). Stir until melted. Remove from heat and cool slightly.

Step 3

Beat the butter and sugar in an electric mixer until thick and pale. Add melted chocolate and mashed potato and beat until smooth. Add the eggs, one at a time, adding a little of the flour each time, beating well after each addition. Fold in the remaining flour, then stir in the milk until well combined.

Step 4

Divide mixture between the 2 pans and bake for 25-30 minutes or until a skewer inserted in the centre comes out clean.

Step 5

Cool for 5 minutes in the pan, then turn out onto a wire rack to cool completely.