Warm the buttermilk to lukewarm, mix the 2 cubes of yeast well in it, put all the other ingredients in a large bowl. Mix with the buttermilk to form a dough. Form into a greased bread pan.
Let rise a little.
Bake at 150 degrees for 2 hours and 45 minutes, the last hour cover with aluminum foil.
Then turn off the oven and rest for 2 hours.