Dissolve half of the yeast with half of the milk (warm). In another container, mix 2.6 oz softened butter with sugar and the remaining milk. Add the milk and yeast mixture, then stir. Then add the sifted flours and salt and knead for 5 or 6 minutes until the consistency is stretchy. Cover and allow to set for 1 hour, until it doubles its volume.
Then roll out the dough using a rolling pin and over a piece of parchment paper, give it a square shape and distribute half the berries on top (after washing and drying them). Divide in two parts, roll each one separately, then together.
Put the dough in whichever mold you prefer (buttered) and set aside for 50 minutes. Brush the surface with beaten yolk and 1 tablespoon of water, then add the rest of the rinsed berries.
Allow to cook for 35 to 40 minutes in the oven preheated to 360°F. Take out, wait for a few minutes, then unmold. Allow to cool over a baking rack, decorate it to your liking and it is ready to serve.