Preparations

1. Leave the butter at room temperature to soften.
2. Preheat the oven to 175°C (347°F) about 10 minutes before using it.

Galette base

1. Place the softened butter in a bowl and add granulated sugar. Mix well until it becomes pale and creamy. Add the egg yolk and mix thoroughly.
2. Sift in the flour and baking powder, add the salt, and mix with a rubber spatula.
3. Pour the dough into a round tart ring and use the back of a spoon to spread it evenly. Bake in a preheated oven at 175°C (347°F) for about 20 minutes. Once cooled, gently insert a knife between the ring and the dough to carefully remove the galette from the mold.

Custard cream

1. In a small saucepan, warm the milk. In a separate bowl, combine the egg yolks, granulated sugar, and vanilla bean seeds, and mix lightly. Then add the cornstarch and mix again.
2. Add half of the warmed milk to the bowl and mix it well to dilute. Then return the mixture to the saucepan and place it over medium heat again. Continuously whisk the mixture with a whisk to prevent the bottom from burning. Keep mixing until the custard thickens and becomes smooth and glossy.
3. Transfer the custard to a baking dish and press a plastic wrap onto the surface to prevent a skin from forming. Chill the custard in the refrigerator.

Assembly

1. Slice the strawberries horizontally into approximately 3mm (0.12 inches) thick slices. Separate them into two sizes, larger and smaller ones.
2. Make the custard cream soft and smooth again by whisking it.
3. Place the galette on a plate and pour half of the custard cream over it, spreading it evenly. *After baking, the galette will have slightly raised edges around the circumference and a depression in the center, resembling the appearance of a tart crust. This makes it easier to fill with cream.
4. Arrange the sliced strawberries starting with the larger ones, overlapping them in a circular pattern around the edge of the galette. Once you've completed one round around the edge, pour the remaining custard into the center, creating a mound shape. Continue arranging the remaining strawberries in the same way, overlapping them from the outside towards the center, and your galette is ready to serve.