In a large bowl, mix yeast and 1 teaspoon salt into one quart lukewarm water. Let stand a few minutes, then add 3 cups flour or flours, or enough to make a stiff batter. Cover and let stand overnight or at least 4 hours.
When ready to bake cakes, dissolve baking soda, baking powder if using, and sugar in hot water or hot mixed water and milk. Stir into batter, then add about 1 cup or enough lukewarm water to make a thin batter. Bake on a hot greased griddle. Use a long thin metal turner to lift edges and check bottoms. When they are golden brown with bubbles forming on top, flip to cook on other side until done.
Save at least 1 cup of batter for the next baking—it will keep in the refrigerator for about a week. To renew, add lukewarm water, salt, and enough buckwheat flour to make a stiff batter. Cover and let stand overnight or at least 4 hours.