Grind Pepper powder, jeera and curry leaves and keep aside. Soak the urad dal in water for 2 hour. Remove the water and spread the dal in cotton cloth. Allow it to dry for an hour or two.
Now dividethe dal into two portions, add one portion of dal in the grinder, to this add 1 tablespoon of butter and grind it. Do not add water. Grind a course mixture. Same way grind the rest of the dal also.
To this mixture add the pepper, jeera powder, curry leaves, rice flour, salt and mix well. Basically the dough will be sticky . We are adding rice flour to make it less sticky, when you mix you will see a ball of batter forming.
Heat oil in a kadai. Apply oil in the hands as the batter will be very sticky. Make small balls of the batter and keep them ready. Now take a ball apply oil and press to thin vadai in plastic paper and make a hole in middle
Deep fry these vadas in oil. Keep oil on a medium flame. You can put 6-8 vadas together. Flip over and remove when they are light brown. Can be kept for 2-3 weeks in air tight container