Crumble yeast cakes into bowl. Add sugar, buttermilk, stirring until dissolved. Stir in butter. Mix and sift flour, salt and baking soda. Stir into first mixture. Allow to rise in a warm place about half hour. Shape as desired, bruch with additional melted butter, sprinkle with poppy seeds and allow to rise again on greased pans until about double in bulk. Bake about 20 minutes in hot oven 200ºC . Makes about 2 doz. rolls.