Dice potatoes into medium cubes.
Heat oil in a pan, sauté chopped onion and ginger paste until golden.
Add chopped tomatoes, turmeric powder, red chili powder, and salt; cook until tomatoes soften.
Add diced potatoes, green peas, and water; cover and simmer for 15 minutes until potatoes are tender.
Garnish with garam masala and serve warm.