1. In the bowl of a stand-up mixer fitted with a paddle attachment, add the butter, egg, sugar and milk and mix until just combined. Switch the attachment to the dough hook, add the flour and knead the dough until it just comes together. Press into a ball, cover in clingfilm and chill for 2-3 hours.
2. Preheat the oven to 170°C, gas mark 3. Roll the pastry out to 3mm thickness and line a 23cm loose bottomed flan tin, trimming the edges and reserving the leftovers. Line the tart case with parchment paper and fill to the edge with baking beans. Bake the tart case for 40 minutes or until golden brown.
3. Meanwhile, prepare the egg wash by blitzing 25g warm, leftover pastry with 1 whole egg and 1 egg yolk. After 30 minutes, remove the baking beans and parchment and brush the tart case with the egg wash. Cook for a further 10 minutes. Remove from the oven and allow to cool.
4. For the crystallised almonds, toast the almonds in the preheated oven for 8 minutes. In the meantime, make a syrup with the sugar and 75g water and bring up to 130°C. Remove the syrup from the heat and add the toasted almonds. Using a whisk, mix the almonds into the syrup until the mixture crystallises. Pour onto a tray lined with baking parchment and allow to cool and harden. Break up into pieces.
5. For the frangipane base, cream together the butter and sugar in a stand-up mixer fitted with a paddle attachment until light and creamy. Slowly add 3 eggs, one at a time. Turn the mixer to slow and add the almonds and flour. Mix well and add the remaining egg, then mix until well combined.
6. Spread the cooled and cooked pastry case with an even layer of cherry jam, then spoon in the frangipane mixture. Bake in a preheated 170°C oven for 25 minutes. Remove the tart from the oven and arrange the cherries and crystallised almonds on top and return to the oven for a further 25 minutes. Cool slightly before removing from the tin.