In a bowl, combine the ragi flour, rice flour, cumin powder, chili powder, sesame seeds (optional), and salt. Gradually add water to form a smooth, stiff dough.
Cover the dough with a damp cloth and let it rest for about 10–15 minutes to make it easier to roll.
Take small portions of the dough and roll them out into thin, flat discs using a rolling pin. The thinner, the crispier!
Use a knife or pizza cutter to cut the rolled-out dough into triangles or square shapes.
Heat oil in a deep pan or wok on medium heat for frying. To check if the oil is ready, drop a small piece of dough—if it sizzles and rises, the oil is hot enough.
Carefully slide the cut pieces of dough into the hot oil and fry them in batches. Fry until they turn golden brown and crispy (about 2–3 minutes).
Remove the chips from the oil and place them on a paper towel to drain excess oil. Let them cool down and crisp up further.