In a large bowl, mix together sourdough starter, buckwheat flour, and milk or buttermilk. Leave on counter top, covered, overnight until bubbly.
To the batter add: baking soda mixed with 1 tablespoon water, egg, pinch of salt and sugar. Stir together. Make pancakes asap after mixing in the baking soda mixture and other ingredients.
Heat griddle until hot, lightly grease.
Pour batter onto hot surface, cook until bubbles appear on the surface and edges of pancakes look dry, flip over and cook until lightly browned.
Serve with sliced fruit of your choice, maple syrup and whipped cream, if desired.