Millet is a great flour to use solo in a simple recipe such as this. It has a very subtle nuttiness while still maintaining a fairly neutral flavor. Throw these biscuits together the night before for breakfast, or after breakfast for supper.
Place millet flour in a medium bowl. Cut in butter until it resembles peas and is crumbly in texture. Pour in gluten-free sourdough starter and buttermilk and mix well until combined.
Cover and let sour 8 to 12 hours.
When ready to bake, preheat oven to 425°F.
In a small bowl, beat eggs. Pour the eggs over the soured dough then sprinkle the baking powder and salt on top.
Mix all ingredients together, using a utensil or your hands if it is too hard to handle. Knead or mix the ingredients together well for a couple of minutes to ensure that everything is well-distributed.
Grease a baking sheet. Use a large soup spoon or tablespoon to scoop heaping tablespoons of dough onto the prepared baking sheet. Leave at least 1 inch of space between biscuits.
Once pan is full, transfer to preheated oven and bake 12 to 14 minutes or until set on top and golden brown on the bottom. Allow to cool completely before transferring. These are a bit crumbly at first, but firm up as they cool.