Peel the pumpkin and sweet potato. Trim the edges of the beans. Cut all the vegetables into little bigger than bite size chunks.
In a medium hot pan, dry roast the cumin seeds, coriander seeds and fennel seeds for a few seconds. Grind it using a mortar pestle or a spice grinder. Keep it aside to be used later.
Paanch Phoron is available in most Indian stores but if you have to make it at home, just mix equal portion of fenugreek seeds, cumin seeds, nigella seeds, black mustard seeds and fennel seeds.
Place a big heavy bottom pan on medium heat and pour the oil. Once the oil heats up, drop the paanch phoron and dry red chili. Let it sizzle for a few seconds. Drop the pumpkin and sweet potato chunks (the idea is to cook the vegetables in intervals, starting with the ones that will take more amount of time to soften). Add the salt, sugar and turmeric. Stir around, cover the pan and cook for 10 minutes, stirring once in between.
After 10 minutes, add rest of the vegetables and stir around. Cover the pan and cook for 5 minutes.
By now, the vegetables should have released juices and softened. Sprinkle the spice powder that was kept aside. Toss around to mix everything and cook for 2 more minutes.
Check for salt and add any, if needed.