Make the pastry cream: Heat 1/2 cup milk (130 ml) in a saucepan until it comes to a boil. Meanwhile, whisk 1 egg yolk with 2 tablespoons sugar (use 1 packet vanilla sugar and 1 tablespoon granulated sugar). Add 1 tablespoon cornstarch. Gradually pour in the hot milk while whisking. Return the mixture to the saucepan and cook, stirring, until thickened. Pour into a dish, cover with plastic wrap directly on the surface, and let cool.

Make the frangipane: Mix 6 tablespoons softened unsalted butter (90 grams) with 7 tablespoons almond flour and 8 tablespoons powdered sugar. Add 1 tablespoon cornstarch and 1 egg yolk.

Fold the cooled pastry cream into the frangipane mixture.

On one sheet of all-butter puff pastry (about 8 inches/20 cm in diameter), spread the frangipane mixture in the center, leaving about a 3/4-inch (2 cm) border. Place the fève (small charm or bean) inside. Cover with the second sheet of puff pastry. Brush the edges with water to seal. Brush the top with egg yolk. Chill for 30 minutes.

Preheat the oven to 350°F (180°C).

Brush the galette again with egg yolk and use a knife to make decorative patterns on top without cutting through the pastry. Poke a small hole in the center. Bake for 50 minutes at 350°F (180°C). If it browns too quickly, cover with aluminum foil to finish baking.

When the galette comes out of the oven, brush with maple syrup or a simple syrup made from 2 tablespoons sugar (30 grams) and 2 tablespoons water (30 grams).