To make the savoury sugar, heat oven to 140C/fan 160C/gas 1. Scatter the muscovado sugar, Maldon sea salt and lemon zest over a baking sheet, then leave in the oven for 15 mins to dry out. Leave to cool, then blitz in a blender. Pass through a large-holed sieve to remove any big lumps, then set aside.
For the pastry, pulse the flour and butter together in a food processor until you have the texture of breadcrumbs. Add the sugar and eggs and pulse until everything comes together. Wrap the pastry with cling film and chill.
Tip the raisins into a pan with the whisky, and add 1 tsp of the sugar. Bring to a simmer, then leave to one side.
Cut the apples into large wedges and melt the butter in a heavy-based pan. Toss the apples in the butter, then add half the demerara sugar, the cinnamon stick and a healthy splash of whiskey. Cook the apples for 3-4 mins until coloured, then place in a sieve to drain away excess juices.
Turn oven up to 160C/fan 140C/gas 3. Grease and flour a 28cm baking ring. Roll two-thirds of the pastry to the thickness of a £1 coin and line the ring. Chill for at least 20 mins. Prick pastry with a fork, then bake blind in the oven for around 10 mins. Brush with beaten egg, then return to the oven for 5 mins. Repeat this process again, cooking for another 5 mins – this will keep the pastry crisp. Leave to cool, then add the apple and raisin mixtures reserving any whiskey that has not been absorbed by the raisins. Roll a lid
for the tart with the remaining pastry and place on top of the tart, egg washing to secure edges. Prick the top to release steam, egg wash the top of the pastry and sprinkle with the remaining demerara sugar. Turn oven to 180C/fan 160C/gas 4 and cook for 20 mins, until the top is golden.
Put the apple tart on a large board. Lightly
whip the cream and add the raisin whiskey to taste. Serve the spiced sugar in a bowl on the
side to sprinkle over.