Heat a large skillet over medium high heat. Add the oil. Once the oil is hot, Add the veggies except peas to the skillet and mix. Let sit for 2 mins then flip. Repeat after another few minutes to brown some edges of the veggies. Mix the turmeric and mustard powder in 1/4 cup water and add to the skillet. Reduce heat to medium . Cover and cook for 12-14 minutes or until the veggies are cooked to preference
Add peas, salt, mix, Cover and reduce heat to low.
Meanwhile, make the spiced oil/ tempering. Heat oil in a small skillet over medium heat. When the oil is hot, add panch phoron spices and let the spices start to pop. 2 mins. (use a lid if the spices pop out too much)
Reduce heat to low, Add asafetida and green chilies and cook for a minute or until the chilies are golden.
Add this tempering to the skillet with veggies and mix in well. Add in sugar if using, and mix. Taste and adjust salt and spice. Add some cayenne if needed for heat. Add a splash of water if the veggies are sticking. Cover and cook for a minute or so to help the flavors meld. Cook uncovered if too wet. Garnish with cilantro and lemon (optional). Serve as a side in Indian meal or in a bowl with Dal and rice or flatbread.
Notes
Pressure Cooker/Instant Pot: Add the first 7 ingredients and 1/4 tsp salt to a pressure cooker/IP and cook at manual low pressure for 4 mins. Meanwhile, make the tempering(steps 3 and 4). Quick release, add the tempering, 1/4 tsp salt and peas and saute for a few minutes. Taste and adjust salt and heat.Nutritional values based on one serving