Preheat the oven to 180 ° C. Mix both types of flour with the following 5 ingredients. Work in the butter with 2 knives until you have a coarse crumble. Add the sultanas (or nuts or kernels) and caraway seeds (to taste) and stir in the buttermilk until a crumbly batter is formed.
Knead the dough a little on a generously floured work surface. Do not knead too long, otherwise it will be tough! Shape into a round loaf or small bun and place on a baking sheet.
Dust the loaf with flour and cut crosswise about 2 cm deep with a knife. Bake for about 1 hour, until the cooking test shows that the bread is done. Let cool down!