Galette des rois à la frangipane

Cook the pastry cream. Whisk the 25 g egg yolk with 25 g sugar and 10 g flour. Heat the 100 ml milk, whisk it gradually into the yolk mixture, return everything to the saucepan and cook over medium heat, stirring continuously, until the custard reaches 82 °C. The pastry cream is thick enough to hold clear whisk trails and reaches 82 °C. Cooking the flour removes a raw taste and gives the custard enough body for a sealed galette. Stir continuously; use a clean thermometer and do not leave egg custard unattended.

Cool and refrigerate the pastry cream. Scrape the hot custard into a shallow tray, cover the surface directly and cool it quickly. Refrigerate until it is 4 °C or below before it touches the almond cream. The pastry cream is cold throughout and has reached 4 °C or below. Cold custard will not melt the butter in the almond cream or soften the puff pastry. Spread in a shallow layer, cover the surface, and refrigerate promptly; keep at 4 °C or below.

Mix the almond cream and fold in the cold pastry cream. Beat the 75 g softened butter with 75 g sugar, work in 75 g ground almonds, then add 75 g beaten egg in stages. Weigh 150 g of the cold pastry cream and fold it through the 300 g almond cream until uniform. The frangipane is smooth, thick and evenly blended with no streaks of pastry cream. The 300 g almond cream and 150 g finished pastry cream give a 2:1 frangipane ratio. Keep the filling cool and return it to the refrigerator if the kitchen is warm.

Assemble and seal the galette. Cut two 24 cm discs from the 500 g cold puff pastry. Put one disc on the lined sheet, spread the frangipane into a 17 cm circle, brush the clean margin lightly with some of the 25 g beaten egg and cover with the second disc. Press out trapped air and seal the rim. The filling forms an even disc about 17 cm across and no more than about 2 cm thick, leaving a clean 3 cm sealing margin. A clean margin and even thickness reduce leakage and help the centre bake through. Keep the pastry cold; do not trap a hidden fève in the galette for children or anyone who may not expect it.

Score, vent and chill the assembled galette. Brush the lid with the remaining egg, score a shallow decorative pattern without cutting through and make a small steam vent. Refrigerate the assembled galette for 30 minutes at 4 °C or below. The top is evenly egg-washed, lightly scored without cutting through, vented, and the pastry feels firm after chilling. Chilling sets the seal and firms the fat layers before baking. Keep the assembled galette refrigerated at 4 °C or below until it goes into the oven.

Bake with a hot start and a lower finish. Bake for 10 minutes at 200 °C, then lower the oven to 170 °C and bake for another 20 minutes. Keep the galette flat on the hot sheet so the base has enough heat to crisp. The galette is deeply golden, the puff pastry is crisp at the base and sides, and the centre is fully baked rather than doughy. The hot start lifts the pastry; the lower finish cooks the centre without scorching the surface. Bake 10 minutes at 200 °C, then 20 minutes at 170 °C.

Cool before slicing. Transfer the galette to a wire rack and leave it undisturbed for 30 minutes before cutting. The galette has settled for 30 minutes and the filling no longer flows when a slice is cut. Cooling lets the frangipane set and protects the crisp layers from steam. Serve the same day for best pastry quality; refrigerate leftovers within 2 hours.