Directions

1. Make the pastry for the base: whizz the flour, almonds, butter and sugar in a food processor to fine crumbs. Add the egg yolk (reserve the white for later) and a few drops of water if necessary, then pulse until the dough comes together. Wrap in cling film, then chill for 1 hr.
2. Heat oven to 200C/180C fan/gas 6. Roll out pastry on a large square of baking parchment, then trim to a 26cm round using a cake tin or plate as a guide. Carefully transfer the pastry still on the paper to a large baking sheet. Bake for 12-15 mins until golden. Cool on the paper, then transfer to a large, flat serving plate. Can be made 2 days ahead.
3. To make the choux pastry, line a large baking sheet with baking parchment. Heat the butter in a pan with 125ml water until melted, then increase heat until boiling. Remove from the heat, then add the flour in one go, quickly stirring until everything comes together as a thick paste. Leave to cool for 10 mins. Beat the eggs in to the paste, using a wooden spoon, a little at a time, until you have a thick, glossy mixture. Spoon 12 equal-size blobs of choux, a little apart, over the baking sheet. Lightly whisk the reserved egg white, then brush over each blob of pastry. Sprinkle with flaked almonds.
4. Bake the buns for 25-30 mins until crisp and golden. Remove from the oven, carefully split each bun, then return to the oven for 5 mins more to dry out the insides. Cool on a rack, then scoop out any soft insides. Can be made 2 days ahead - if they go soft, briefly crisp them up in the oven.
5. To make the filling, mix the custard powder and sugar in a pan, then blend in a little milk to a smooth paste. Add the rest of the milk, then gently bring to the boil, stirring, until you have a thick custard. Remove from the heat, then stir in the vanilla. Transfer to a bowl, then cover the surface with cling film. Cool. Can be made 2 days ahead.
6. Now assemble the gateau: stir the custard to loosen a little. Whip the cream to soft peaks, then fold into the custard. Slice a third of the strawberries. Spread a thin layer of custard over the pastry base. Add the sliced strawberries to the remaining custard, then use to fill the choux buns. Arrange buns around edge of the pastry base. Spoon any remaining custard into the centre, then top with the remaining strawberries.
7. To make the caramel, tip the caster sugar into a heavy based pan with 2 tbsp cold water. Heat, without stirring, to dissolve the sugar, tipping the pan if necessary, then boil hard until it becomes a light caramel. Remove from the heat and, when the bubbles subside, drizzle carefully over the choux buns. Dust with icing sugar and serve. The gateau can be chilled for up to 2 hrs before serving.