Serve with the Indian flatbreads known as chapatis for a vegetarian meal or use as an accompaniment for simple grilled fish or chicken. If you'd like a hotter taste, do not remove seeds from the jalapeño pepper.
Place potatoes in a large saucepan and cover with water. Add salt and bring to a boil. Cook over medium heat until the potatoes are tender, 10 to 20 minutes. Drain and cool slightly. Crush the potatoes with the back of a wooden spoon and set aside.
Meanwhile, toast cumin, coriander and cardamom seeds in a small dry skillet over medium heat, stirring, until aromatic, about 1 minute. Transfer to a spice mill or mortar and pestle; grind to a powder. Add turmeric and cinnamon; set aside.
Heat oil in a large nonstick skillet over medium heat. Add yellow and brown or black mustard seeds and cover the pan; when the seeds start to pop, remove the pan from the heat and let stand until the popping ceases. Uncover the pan and return to low heat. Add onions and saute until golden, 10 to 15 minutes.
Add garlic, jalapenos, ginger and the reserved spice mixture and saute for 2 minutes more. Stir in water and simmer for 5 minutes. Stir in peas, mint and lemon juice and cook until heated through, about 3 minutes. Stir in the reserved potatoes and season with salt and pepper.
2 1/2 starch, 1 vegetable
I followed the recipe to the letter. The curry came out too spicy and was overwhelmed with mustard flavor. It should perhaps be read as 1/2 teaspoon mustard.