In a stand mixer fitted with the dough hook, combine the flour, sugar, and yeast. Add the milk or sour cream, egg, and vanilla, and mix on low until a dough forms. Add the salt and mix for a few minutes. Gradually add the butter and mix until the dough is smooth and elastic. Shape into a ball, cover, and refrigerate for 12 hours.

To make the filling, combine the softened butter, vanilla, cinnamon, and salt until smooth. Add the powdered sugar and mix until creamy, then stir in the almond flour until fully incorporated.

Grease a 12-inch/30-centimeter round pan. Roll the chilled dough into a large rectangle. Spread the almond filling evenly over the dough. Fold the top third of the dough toward the center, then fold the bottom third over it. Gently roll the dough into a smaller rectangle.

Cut the dough into strips. Slightly stretch each strip, twist it, and roll it into a coil. Arrange the coils in the prepared pan, cover, and let rise in a turned-off oven for about an hour.

Brush the risen pastry with beaten egg, then scatter the berries and sliced almonds on top. Preheat the oven to 350°F/170°C convection and bake until golden and cooked through. Cool, dust with powdered sugar, and serve.