Peel and cube the potatoes (about 3/4 inch cubes). Dice the onions

Place peeled and cubed potatoes into a large pot and cover with salted water. Bring to a boil over high heat, then reduce heat to medium-low, cover, and simmer until just tender, about 15 minutes. Drain and allow to steam dry for a minute or two.

Meanwhile, heat the butter in a large skillet over medium heat. Stir in the onion and garlic; cook and stir until the onion has softened and turned translucent, about 5 minutes. Season with cumin, curry powder, garam masala, ginger, and salt; cook for 4 minutes more. Add the tomatoes, garbanzo beans, peas, and potatoes. Pour in the coconut milk, and bring to a simmer. Simmer 10 to 20 minutes before serving.