In a mixing bowl, lightly whisk the egg yolks together with the sugar, vanilla bean paste and sea salt. Add the softened butter, beat until creamy and smooth. Combine the all-purpose flour and baking powder. Mix until smooth.
Pour your batter into the Flexipan®, flatten the top with the back of your spatula. Then, brush your egg yolk and use a fork to design the top.
BAKE!
Bake for 35 minutes at 350F/180C. (Every oven heats differently, monitor your cakes from 30min). It is ready when the toothpick inserted comes out clean.
Once your Gâteau Breton (French Buttery Cake) is out of the oven, let it completely cool down before unmolding directly onto your cooling rack. Enjoy & Bon Appétit!