Parry the venison well and cut into slices about 5 mm thick. Rinse the sage, shake dry and chop finely. Remove the skin from the onion and cut into half rings, clean the mushrooms. Season the meat with salt and fry in a hot frying pan with clarified butter, remove and keep warm.
Sauté the blackberries in the same frying pan, caramelize with sugar and keep warm as well.
Fry the mushrooms in a frying pan with 2 tbsp butter, then add the sage and onion, season with salt and sugar, extinguish with chicken stock and cook by about half. Mix in 1 tbsp cold butter and thicken the sauce with it. Add meat and blackberries to the sauce form, toss and bring to the table. Serve with a nut brioche.
For the brioche, put flour, 1 pinch of salt, egg and soft butter in a suitable bowl. Melt the yeast in the milk, add to the flour form and knead into a smooth dough. Leave the dough in a warm place with the lid closed for about half an hour.
Chop the nut mixture and mix into the dough.
Preheat the oven to 180 °C (convection oven 160 °C ). Form four small loaves from the dough. Form them on a baking tray lined with parchment paper and bake in the oven for about 15 minutes.
By the way: Did you know that clarified butter is obtained by extracting water, milk protein and lactose from butter?