Preheat the oven to 180°C/fan160°C/gas 4. Grease a square 20cm loose-bottomed cake tin and line the base with baking paper.

Cream the butter and sugar until very light. Beat the egg yolks and add to the mixture, a little at a time, beating well. Fold in the ground almonds, milk and melted chocolate.

Whisk the egg whites to soft peaks. Using a large metal spoon, carefully fold a third into the chocolate mixture. Once well mixed, fold in the rest, then fold in the flour. Spoon into the prepared tin, level the surface and bake for 35 minutes.

Prick the top of the cake all over with a skewer and spoon over the chocolate toffee sauce. Gently spread over the top and return to the oven for 5 minutes. Cool in the tin for 5 minutes, then slide or lift out. Cut into squares and serve hot or warm with crème fraiche.