Before you start: put the butter in the freezer for at least 2 hours. The pastry will only work if it is very cold.
Put the flour and the salt in a large bowl. Take the butter out of the freezer and grate on the big holes of a box grater, so that the butter falls into the bowl. Stop from time to time and, using a knife, toss the butter flakes in the flour, so that they don’t clump together.
In a jug, mix the ice cold water with the lemon juice. Add most of the liquid to the flour mix, pouring it in a thin stream in a circular motion around the bowl while mixing with the knife – so that the dough gently comes together. Using your hands, pat the dough together – don’t knead! If it seems too dry and it doesn’t hold, add a tiny bit more water. You don’t want this to be a wet dough, but crumbly and not smooth.
Divide the pastry into 2 portions, shape into discs and wrap in cling film. Put in the fridge for at least 1 hour or overnight.
While the pastry is resting, make the filling. Put the ground almonds in a bowl with the butter and sugar and mix to a paste. Add the eggs, flour, Amaretto, lemon zest and salt and mix again. Fill into a piping bag and put in the fridge for at least 1 hour.
Once the pastry and filling have chilled, preheat your oven to 220°C fan.
Separate the remaining egg: put the egg white into a small bowl, and mix the egg yolk with a tablespoon of milk in a second small bowl.
Flour your surface and take out one pastry disc. Roll it out to a 30 cm disc, dusting the pastry surface lightly with flour if it sticks to the rolling pin. Lift the pastry onto a baking tray lined with baking paper.
Spread the jam all over the pastry, leaving a 2 cm border around. Then pipe the filling over the jam, spreading it with a spatula in the end to make it even. Stick an almond or bean into the filling.
Brush the exposed border of the pastry disc with egg white.
Roll out the second pastry to a 30 cm disc. Roll the pastry back over your rolling pin and lift it onto the filled disc, pressing the edges so they stick.
Cut off the uneven dough around the edges of the pastry, so that it makes a neat, round disc. Then, press and crimp the edges with your fingers.
Cut three holes into the middle of the pastry, then score a shallow pattern across the top of the pastry, making sure not to cut all the way through the pastry.
Brush the top of the pastry with the egg yolk.
Bake the galette in the middle of the preheated oven for 40 minutes. There will be quite a lot of butter melting out of the pastry, but this is normal.
When the galette comes out of the oven, lift it with the baking paper onto a wire rack. Leave to cool completely before serving.
