In a large mixing bowl, combine the all-purpose flour, whole wheat flour, achar masala, and salt if using. Gradually add water and knead into a medium-firm dough. The dough should be pliable but not too soft.
Pinch off small portions of the dough and roll each one into a thin disc using a rolling pin. For uniformity, you can use a cookie cutter to cut the rolled dough into neat circles, or alternatively, a sharp-edged lid works well for cutting perfect rounds.
Use a fork to prick the surface of each disc, preventing them from puffing up during frying.
Heat oil in a deep pan over medium heat. To test if the oil is ready, drop a small piece of dough into it; it should sizzle and rise steadily. Fry the discs in batches, ensuring the oil remains consistently medium hot — too cold, and the mathri will develop bubbles; too hot, and they will turn soft instead of crisp.
Once golden and crisp, remove the mathris and place them on paper towels to absorb any excess oil. Allow them to cool completely before storing.