In a mixer, add roasted, skin peeled peanuts and powder it coarsely. If you are using store bought roasted peanuts, then skip the above roasting step.
Next, take jaggery and 3 tsp of water together in a pan and cook it in medium flame. When jaggery dissolves completely in water, add grated coconut and stir for few minutes.
When the coconut gets cooked for a minute, add in powdered peanuts and stir. Switch off and let it cool.
Next heat rice powder in a wide pan till warm. Transfer it in to a wide bowl, add around 3/4 cup of hot water. Combine and knead a soft dough. Ensure there is no crack in the dough.
Divide the dough and peanuts stuffing in to 15 equal balls and keep them ready.
Take a dough ball, pressing it through your fingers widen it to 2" diameter disc. Keep peanuts stuffing in the middle and bring the ends together to seal it. Keep this in a modak mould and press it.
When the modak mould it pressed like this, it will leave impression over the dough giving nice texture. Remove carefully and arrange in a steamer plate. Repeat the process with rest of the dough.
Steam cook the modak for about 10 to 15 minutes and offer to God as naivedyam.
Delicious peanuts stuffed modak.