Scald and then rinse out with cold water a large stone crock. Pour in milk, water, and sugar. Crumble in yeast cake and stir until dissolved. Add the prepared buckwheat flour. Beat to thoroughly mix. Cover and set aside overnight to rise.
In the morning add sufficient lukewarm water to bring the mixture to a pouring consistency. This usually requires about one cupful. Add syrup. Beat hard for three minutes and then let stand in a warm place while the griddle is heating, then bake.