Mimosa cake

Preheat the oven to 160ºC, gas mark 3. Grease and line 2 x 18cm round cake tins. Crack the eggs into the bowl of a freestanding mixer (or use a large bowl and electric beaters). Add a pinch of salt and whisk, slowly adding the vanilla seeds (reserve the pod) and sugar. Whisk at a medium speed for 15 minutes. Gently fold in the cornflour, pasta flour and lemon zest until all combined. Divide the mixture between the prepared tins. Lower the oven to 140ºC, gas mark 1, and bake the sponges on the bottom shelf for about 50 minutes, until a skewer inserted into the centre comes out clean. Turn out onto a wire rack to cool.

Meanwhile, for the custard, cut the reserved vanilla pod into 5 pieces. Put in a medium pan with the milk and zest. Set over a mediym heat and bring to the boil, stirring occasionally. Put the egg yolks, surar and flours in a large bowl. Using a balloon whisk, mix to a creamy and smooth consistency. As son as the milk reaches boiling point, strain it through a sieve over the gg mixture, whisking to combine. Discard the zest and vanilla. Tip everything back into the pan; stir continuously over a gentle heat until thickened (about 15 minutes)/ you can use the custard straight away or cover the surface directly and keep chilled.

For the syrup, mix the rum (or juice), sugar and 130ml water in a small pan. Cook, stirring, until the sugar has completely dissolved, then pour into a bowl and set aside to cool.

When the sponges have cooled, use a serrated knife to remove the golden crusts (the edges and upper and lower layers) until you're left with only the central part of the sponges (reserve the crusts). Take one of the cakes and slice horizontally into 3 discs of equal thickness. Put the first layer of sponge on a serving plate, spread over a little syrup, then top with ¼ of the custard. Repeat with two more layers of sponge, syrup and custard. Use a spatula to coat the edges of the cake with the remaining custard. In a food processor, whizz the sponge crusts into fine crumbs. Cut the other cake into 0.5-1cm cubes. Scatter the cubes of cake over the entire surface of the cake, then sprinkle over the crumbs. Cover with an upturned bowl and chill for 3 hours before serving.