Prepare the Potatoes: Boil the potatoes in their skins until fork-tender.
Once cool enough to handle, peel if desired and cut into ½-inch (1. 5 cm) pieces.
Set aside.
Make the Spice Paste: In a spice grinder or mortar, grind the cloves, peppercorns, coriander, cumin, and fennel seeds into a fine powder.
Transfer this to a blender with the ginger, green chilies, 1 tbsp (15 ml) of fresh coriander, and water.
Blend to a smooth paste.
Temper the Spices: Heat the ghee (or oil) in a large nonstick skillet over medium-high heat.
Once shimmering, add the mustard seeds and let them pop and turn gray. If using the oil/butter combo, add the butter now.
Build the Sauce: Carefully add the curry leaves, followed by the chopped tomatoes and turmeric.
Reduce heat to medium and cook, stirring, until the tomatoes soften and the oil begins to separate from the mixture.
Add Flavor: Stir in the prepared spice paste and cook for 1-2 minutes until fragrant. This step is crucial to cook out the raw flavors.
Finish the Dish: Gently fold in the cooked potatoes, garam masala, chat masala, and salt.
Stir to coat everything evenly.
Cover and cook on low for 3-5 minutes, until the potatoes are heated through.
Garnish and Serve: Sprinkle with the remaining 2 tbsp (30 ml) of fresh coriander and serve hot.