Grind the almonds to a coarse texture in a food processor.
Put the ground almonds, ‘00’ flour, polenta, vanilla extract and 50g/1¾oz sugar in a bowl, then roughly rub in the butter. Spread the mixture out on a baking tray, cover and put in the fridge for 1 hour. Preheat the oven to 180C/Fan 160C/Gas 4.
Bake the crumble for 10–20 minutes, but check from time to time to make sure the edges aren’t burning. Leave to cool, then break up into crumble.
Meanwhile, pour the milk into a medium heavy-bottomed saucepan, add the vanilla pod and bring to the boil.
Separate the whole eggs and whisk the six yolks with 75g/2¾oz sugar in a large, heatproof bowl. Stir in the plain flour to make a paste. Pour over the hot milk, whisk well, then return to the saucepan over the heat. Reduce the heat and cook gently for 5 minutes, or until thickened. Pour into a bowl, then cover and chill.
Spoon 4 tablespoons of the cold custard into a small bowl and add a dash of milk to let it down. Set aside.
Meanwhile, cook the Bramley apples in a little water with a 100g/3½oz sugar and half the lemon juice, until smashed to a purée. Cook the Cox’s apples in a little water with 50g/1¾oz sugar and the remaining lemon juice until soft but holding their weight.
Spoon the apple puréeonto a plate, cover with the softened diced apple, scatter over the raspberries, then spoon over the cold custard.
Whisk the eight egg whites and the remaining 75g/2¾oz sugar in a clean, glass bowl until thick. Stir in the reserved 4 tablespoons custard.
Spoon the egg white mixture over the fruit and glaze using a blow torch. Sprinkle over some crumble mixture and serve.