Peel and dice potatoes into 1/2–3/4-inch cubes so they cook evenly. Chop carrots and green beans into similar-sized pieces; measure peas. Finely chop the onion and tomato (or puree the tomato). Prepare ginger-garlic paste and slit green chilies if using.

Tempering and building the masala

Heat oil and seeds

Warm a heavy skillet or Dutch oven over medium heat. Add 3 tbs oil/ghee. When hot, add mustard seeds and cumin seeds. Once they sputter (about 20–30 seconds), add curry leaves and a pinch of asafoetida if using; stir briefly until fragrant.

Cook onion

Add the finely chopped onion and a pinch of salt. Sauté on medium heat for 6–8 minutes until the onions are soft and lightly golden, stirring occasionally to prevent sticking.

Add aromatics and tomato

Stir in 1 tbs ginger-garlic paste and the slit green chili; cook 1–2 minutes until raw smell subsides. Add the chopped or pureed tomato and cook for 4–6 minutes until the tomato breaks down and oil begins to separate around the edges.

Spice the masala

Lower heat slightly and add 3 tsp turmeric, 1 tsp red chili powder, 1.5 tbs coriander powder and 1.5 tsp salt. Mix well and cook the spices with the onion-tomato mixture for 2–3 minutes to roast the spices and reduce rawness.

Cooking the vegetables

Add potatoes and mixed vegetables

Add the cubed potatoes (3 cups) and 1.5 cups mixed vegetables to the masala. Stir thoroughly to coat all pieces with the spice mixture so they absorb the flavor.

Add liquid and simmer

Pour in 1 cup water or vegetable broth, stir, and bring to a gentle boil. Reduce heat to low, cover with a lid, and simmer for 12–15 minutes until the potatoes and vegetables are tender when pierced with a fork. Stir once or twice during cooking to prevent sticking and ensure even cooking. If the mixture becomes too dry before vegetables are tender, add up to 1/4 cup more water.

Finish with garam masala and adjust seasoning

When vegetables are tender, remove lid and increase heat to medium-low. Sprinkle 1/2 tsp garam masala and gently fold in. Taste and adjust salt or chili if needed. Cook uncovered 2–3 minutes so any excess liquid evaporates and the masala coats the vegetables.

Garnish and serve

Turn off heat. Stir in 1 tbs lemon juice and 1/4 cup chopped cilantro. Cover briefly for 1 minute to let flavors meld, then fluff gently with a spoon. Serve hot as a side or main with rice, roti, or bread.