Combine the sourdough starter, buckwheat flour, rice flour and milk in a medium mixing bowl. Combine with a fork until all ingredients are hydrated. Cover and allow to ferment overnight at room temperature.
In the morning, preheat a griddle pan or skillet over medium heat.
Uncover the fermented batter and mix lightly with a fork to break up a bit. Make a well in the middle.
Crack the eggs into the well and beat. Add the vanilla and salt and begin incorporating the egg mixture into the surrounding batter.
Once the dough is nearly mixed, sprinkle the baking powder over the top and stir until completely combined.
When the griddle is hot, great it lightly with butter, lard or coconut oil. Ladle 1/3 cup of the batter onto the griddle to form a pancake. Cook for 2-3 minutes until small bubbles just begin to appear and the edges begin to firm.
Carefully flip and cook an additional 2 minutes or until golden brown.
Serve piping hot with butter and jam, syrup or honey.
To make a gluten free sourdough starter: Days 1 - 3: In a quart jar, combine 1/2 cup of gluten free flour such as teff, sorghum, or buckwheat, and a scant 1/2 cup of water. Mix vigorously to incorporate air. Cover with a clean cloth and secure with a rubber band. Leave at room temperature for 12 hours. Repeat feedings with the same amounts of flour and water. Days 4 - 7: Continue to feed every 12 hours and discard half of the starter before very feeding. You can add the discarded starter to any quick bread recipe, crepes or fritters.