Warm buttermilk, salt and syrup in a small pot lukewarm. Take it off the stove. Mix yeast and 6 tablespoons of lukewarm buttermilk and add it again to the remaining buttermilk. Mix flour, grist, linseed, sesame and sunflower seeds in a mixing bowl.
Add the buttermilk and yeast mixture and knead well with the dough hooks of the hand mixer. Pour the dough into a greased, flour-spread box form (25 cm long, 11.5 cm wide, 7.5 cm deep). Bake in the preheated oven (electric: 175 °C/ gas: level 2) for approx. 2 hours on the middle shelf. Remove from the oven, let it cool down on a grid and then turn out of the form