Boozy inside-out trifle cake

Method

1. For the syllabub, put everything except the cream in a large mixing bowl to infuse for a few hours.
2. Preheat the oven to 170°C/fan150°C/gas 3½. Line a greased 20cm loose-bottom deep cake tin with baking paper and wrap a double layer of baking paper around the outside, secured tightly with string (this will keep the outside of the sponge from getting too dark).
3. For the sponge, beat the butter, sugar and vanilla in a mixing bowl until light and fluffy. Beat in the eggs, one at a time, adding some of the flour if it looks like it might curdle. Beat in the milk and sherry until smooth. Stir in the remaining flour until the mixture is smooth and well combined. Spoon into the prepared tin and level the surface.
4. Bake for 60-70 minutes or until a skewer pushed into the centre comes out clean. Cool in the tin for about 20 minutes, then turn out and cool completely on a wire rack.
5. Meanwhile make the custard. Put the milk, cream and butter in a pan and, as it comes to the boil, remove from the heat. In a small bowl, mix a little of the hot milk mixture into the cornflour. Whisk the egg yolks with the sugar and vanilla in a large bowl until combined. Whisk the cornflour mixture into the rest of the hot milk, then pour over the egg mixture and stir to combine.Tip into a clean pan and cook over a low heat, stirring all the time, for about 5 minutes until it thickens to a dropping consistency (it stays on a spoon for a couple of seconds, then drops off). Pour into a bowl and whisk until cooled slightly. Leave to cool completely with a piece of cling film touching the surface to prevent a skin forming.
6. Put a 17cm plate or saucer on top of the sponge, in the centre, and cut around it with a small sharp knife to a depth of 4cm. To hollow out the sponge, make a series of cuts 4cm deep inside the circle to create 2.5cm squares, then use a small spoon to scoop it out in blocks. Don’t worry if it’s not perfectly flat – you can even it up when all the pieces have been removed.Drizzle the hollowed-out sponge generously with sherry (freeze the offcuts for making trifle or cake pops). Scatter the raspberries over the hollow, then pour over the custard. Chill for 2-3 hours to set the custard.
7. To decorate, scatter the pistachios over a lightly oiled baking tray. Melt the caster sugar in a frying pan over a low heat without stirring until it forms a golden caramel, then pour onto the pistachios, tipping the tray to coat evenly. Leave to cool completely, then tip out the caramel and carefully break it into shards with the point of a heavy knife.
8. To finish the syllabub, pour the cream onto the boozy lemon and sugar mixture and whisk with a balloon whisk until the cream is billowy and holds its shape. Spoon it over the filled sponge, scatter over pomegranate seeds, then decorate with shards of pistachio brittle. Serve immediately. The cake will keep for up to 2 days in the fridge.