Wash the sweet potatoes, peel them, and cut into uniform 1.5‑cm cubes; set aside in a bowl of cold water for 5 minutes to remove excess starch.

Pre‑heat the oven to 200°C (392°F). Meanwhile, gather all spices, chop the green chili, and finely chop the coriander leaves.

Heat a small skillet on medium flame. Add the cumin seeds and dry‑roast for 30 seconds until they turn aromatic, then grind to a fine powder using a mortar‑pestle – this is your roasted cumin powder.

Drain the sweet potato cubes, pat dry, then toss with mustard oil ensuring each piece is lightly coated. Spread in a single layer on a baking tray and roast in the pre‑heated oven for 20‑25 minutes, turning once halfway, until the edges turn golden‑brown and a fork slides in easily (medium‑low flame equivalent).

Transfer the hot roasted sweet potatoes to a large mixing bowl. Add fresh lemon juice, the freshly ground roasted cumin powder, dry mango powder, rock salt, and the finely chopped green chili.

Place the bowl over a low flame (dheemi aanch) for 2 minutes, gently tossing with a wooden spoon so the spices warm and coat every cube evenly; you’ll hear a faint sizzling and smell a burst of citrus‑cumin aroma.

Turn off the flame. Sprinkle the chopped coriander leaves over the chaat and give one final gentle toss to distribute the herb freshness.

Cover the bowl with a clean kitchen towel and let the chaat rest for 3 minutes so the flavors meld and the lemon juice penetrates the potatoes.

Serve the Shakarkandi Chaat in small bowls or on a banana leaf, optionally garnish with a wedge of lemon for extra zing.

Enjoy hot, paired with a glass of chilled chaas (spiced buttermilk) or a steaming cup of masala chai for an authentic Delhi street‑food experience.