Slice capsicums in half lengthwise and remove seeds.
Boil, mash potatoes, and sauté with 1 tbsp oil, chopped onion, ginger paste, green peas, turmeric, garam masala, and salt.
Stuff potato mixture tightly into capsicum halves.
Heat remaining oil in a pan, place stuffed capsicums face up, cover, and cook on low flame for 12 minutes.
Turn occasionally to roast all sides gently until tender.