In a pan, add 2 tbsp oil, ½ tsp mustard seeds, a pinch of hing, ½ tsp urad dal, ½ tsp chana dal, 2 tbsp peanuts, and some curry leaves. Sauté well.
Add 3 chopped green chilies, 1 tbsp chopped ginger, 1 tbsp chopped garlic, and 1 cup sliced onions. Sauté until translucent.
Add ½ tsp turmeric powder and mix well.
Add ½ cup water and bring it to a boil.
Add 2 cups or 3 medium-sized boiled potato pieces, salt, and ½ tsp sugar. Mix well and cook the masala on a low flame for 5 minutes.
Add 1 tsp lemon juice and some coriander leaves, and mix well.
Dosa masala is ready.