Make the pastry by pulsing the butter and flour together in a food processor.
Add the icing sugar and the egg yolk and pulse a few times until the mixture come together. Use extra water if needed.
Bring the dough together into a ball and flatten it. Wrap it in cling film and let it rest in the fridge for 30 minutes.
Wash and hull the strawberries and quarter or halve them, depending on their size. Mix with the vinegar and sugar for a few minutes.
Line a baking tray with baking parchment and preheat the oven to 180 C or 355 F, Gas Mark 5.
Take the pastry from the fridge and unwrap carefully, leaving it on the cling film. Cover with another sheet of cling and roll out to 30cm round.
Place the pastry on the parchment and scatter the ground almonds over the base about 5cm from the edge.
Drain the strawberries over a sieve and then spoon the strawberries over the almonds.
Fold the pastry into the middle, working around the galette.
Brush the pastry with beaten egg and sprinkle with remaining sugar.
Bake for 30 minutes until bubbling.
Leave to cool completely before moving the strawberry galette to a plate.