Mix all the cake ingredients in a food processor for 5 minutes. Pour into a cake tin 26cm/10½in diameter and bake at 160C/325F/Gas 3 for 45 minutes.
Check to see if the cake is cooked, then remove from the oven and allow to cool for 10 minutes in the tin before removing and placing it on a cooling rack.
For the topping, place the cream cheese, sugar and butter into a mixing bowl and cream together until smooth and soft. Spread over the cake using a palette knife.
For the ice cream, cream together the egg yolks and the sugar until white and stiff.
In a saucepan combine the milk, milk powder and cream and bring to the boil. Pour some of the milk onto the creamed eggs and sugar, whisking continuously.
Return the mixture to the saucepan and over a medium heat cook out to 80C/175F. Pass through a sieve and then pour in the melted white chocolate. Turn in an ice cream machine. Remove and place into the freezer.
Serve each portion of cake with a scoop of the white chocolate ice cream.
Type the ingredients you want to use, then click Go. For better results you can use quotation marks around phrases (e.g. "chicken breast"). Alternatively you can search by chef, programme, cuisine, diet, or dish (e.g. Lasagne).
James Martin is joined by chefs Alyn Williams and Tom Kitchin, and actor Danny Mays.