Soak 1 cup of rice in water for about 2 hours. Drain the water and spread the rice on a cloth to dry. Once dried, grind it into a fine powder.
In a pan, dry roast 2 tablespoons of urad dal until it turns golden brown. Grind it into a fine powder.
In a large bowl, mix the rice flour, urad dal powder, 1 teaspoon of asafoetida, 1 teaspoon of red chilli powder, 1 teaspoon of sesame seeds, and salt to taste.
Heat 2 tablespoons of butter and add it to the mixture. Mix well until the mixture resembles breadcrumbs.
Add water gradually and knead into a soft dough.
Divide the dough into small balls and flatten them using your palm or a flat surface.
Heat oil in a kadai for deep frying. Once the oil is hot, drop the flattened dough into the oil and fry until they turn golden brown.
Drain the thattai on a paper towel to remove excess oil. Let them cool before serving.