You can make homemade puff pastry, or use store-bought. You need two circles at least 27 cm wide.

Make the praline cream

• Mix the sugar and softened butter until smooth and creamy.
• Add the eggs one at a time, then add the ground toasted hazelnuts, and finally the praline paste.
• Put the cream into a piping bag and let it rest in the fridge.

Assemble

• Roll out the puff pastry and cut two 27 cm circles.
• Pipe the hazelnut cream onto the first pastry circle, leaving 1 to 2 cm (½–¾ in) around the edge.
• Brush the edge with a little water, then place the second pastry circle on top to cover the filling.
• Seal the two circles and press lightly with your fingers without crushing the edges.
• Brush the top with an egg yolk + crème fraîche egg wash, then chill for at least 10 minutes (longer if you have time).
• Repeat the egg wash 1 to 2 more times if you like a darker colour. For a lighter colour, one coat is enough.

Bake

• Preheat the oven to 220°C (static heat), or bottom heat (I find fan ovens can be tricky, so even with a modern electric oven, I prefer traditional baking).
• While the oven heats, score patterns on top with a sharp knife without cutting too deeply into the pastry.
• Make “chimneys” by poking 5–6 holes with a toothpick so steam can escape.
• Bake the galette in the hot oven on the lowest rack, using bottom heat, for 10 minutes.
• Lower the temperature to 180°C and move the galette to the second rack, still using bottom heat, and bake for at least 30 minutes. If it browns too quickly, cover with aluminium foil.
• Make sure the galette is fully baked underneath to get a beautiful golden finish on top.