Place the cubed potatoes in a large saucepan and add enough cold water to cover them by 2 cm / 1 inch. Add 1 teaspoon of salt. Bring to a boil over high heat, then reduce the heat to medium. Simmer for 12 to 15 minutes, until the potatoes are tender when pierced with a fork but still firm in the center. Drain the potatoes thoroughly in a colander.

Spread the drained potato cubes onto a large plate or baking sheet in a single layer. Let them cool completely at room temperature for 10 minutes. This allows the surface moisture to evaporate and firms up the potato starch.

Heat 3 tablespoons of cooking oil in a wide skillet over medium-high heat. Add the cooled potato cubes in a single layer. Fry for 15 to 18 minutes, turning them occasionally with a spatula, until all sides develop a deep golden-brown, crispy crust. Turn off the heat.

Transfer the hot, crispy potatoes immediately to a large mixing bowl. Sprinkle the chaat masala, roasted cumin powder, Kashmiri red chili powder, and black salt over the hot potatoes. Toss gently for 1 minute until the potatoes are evenly coated in the spices.

Drizzle the green chutney, sweet tamarind chutney, and fresh lemon juice over the spiced potatoes. Add the chopped fresh coriander, green chili (if using), and ginger juliennes. Toss gently for 1 minute to combine. Transfer to serving plates and garnish with fine sev and pomegranate seeds if desired. Serve immediately.