Mix sourdough starter, flour, milk, and salt together. Knead for a few minutes.
Cover and allow to rise for for 2-4 hours (or overnight for long fermentation).
Divide into 8 equal pieces.
Roll flat (about ¼” thick) on a lightly floured work surface.
Add a small amount of olive oil to a cast iron skillet and preheat over medium.
Cook each flatbread for a minute or two on each side until it starts to brown a bit.
