For the pear and perry crumble, preheat the oven to 190C/375F/Gas 5.
Place the flour and 50g/2oz of the butter into a bowl and rub together with your fingertips until the mixture resembles breadcrumbs. Stir in the ground cinnamon and sugar.
Tip the mixture onto a baking tray and bake in the oven for 10-12 minutes, or until toasted and golden-brown.
Meanwhile, heat the remaining butter in a lidded frying pan until foaming, then add the pears. Fry for 1-2 minutes, then add the perry cider and bring the mixture to the boil. Reduce the heat until the mixture is simmering, cover and cook for 3-4 minutes, or until the pears are softened.
Spoon the pear mixture into an ovenproof dish and sprinkle over the crumble topping. Bake in the oven for 3-4 minutes.
Meanwhile, for the cinnamon custard, heat the cream, milk and cinnamon sticks in a saucepan until just boiling, then reduce the heat and simmer gently for 5-6 minutes.
Beat the egg yolks and sugar together in a bowl, then gradually add the warm cream mixture, whisking continuously. Return the custard mixture to the saucepan and cook over a low heat for 3-4 minutes, stirring constantly, until the mixture has thickened enough to coat the back of a spoon. Discard the cinnamon sticks.
Serve the pear crumble in bowls with a spoonful of cinnamon custard and a scoop of vanilla ice cream.