Mix yeast, 2tablespoons of the milk, 1teaspoon sugar and 2tablespoons flour. Let this starter mixture rest for 10 minutes.
Mix 6tablespoons milk, the egg yolks, salt, 2teaspoons sugar and remaining flour. Mix well and stir into the starter dough.
Add 2tablespoons of the melted butter, little by little, to the dough, and knead it in until well incorporated. Let the dough rise for 1 hour. Preheat oven to 350°F.
Cut dough into walnut-sized pieces. Butter a large baking pan and bake these little biscuits in the preheated oven for 12 to 15 minutes, turning the biscuits to make sure all sides are brown. Set aside.
Bring to a boil remaining milk, butter and sugar. Add vanilla bean, lemon rind and poppyseeds; mix well.
Pour hot water over the biscuits. When they are softened, drain and add biscuits to the milk and poppyseed mixture. Bring it to a simmer over very low heat. Remove from heat.