In a non-reactive bowl (glass or porcelain), whisk together teff and whole wheat flours. Add the sourdough starter and water. Mix well to make a smooth batter with no lumps. Cover with a plate or kitchen towel and set aside at room temperature (72~74°F) for at least 20~24 hours. Batter should be bubbly and smell slightly sour when ready.
1½ cups Teff flour, ½ cup Whole wheat flour or All purpose flour, 1 cup Sourdough starter, fed, 2½ cups Water