Mix mashed potatoes, salt, cayenne, turmeric, cilantro, and 3 tablespoons vegetable oil in a bowl until well combined. Add flour, a little at a time, and knead until a stiff but pliable dough forms; if dough becomes too stiff, add a few drops of water.

Transfer dough to an oiled bowl and turn to coat. Cover with plastic wrap and set aside for 10 minutes.

Preheat a nonstick griddle to medium heat.

Divide dough into eight lemon-sized portions and roll out on a lightly floured surface to a 1/4-inch thickness.

Working in batches, fry chapatis on the hot griddle using up to 1 teaspoon of oil for each side. Cook until brown spots have started to form on the bread and the dough is cooked through.