In a small skillet over medium-high heat, toast the cumin, coriander, cloves and peppercorns until fragrant, about 1 minute. Transfer to a spice grinder or mortar and grind. Add tumeric, paprika, and cinnamon, set aside.
In a large, deep skillet or dutch oven heat the oil over medium-high heat. Add the mustard seeds, shallots and serrano pepper with a pinch of salt and pepper and sautee until the shallots begin to brown, about 5 minutes.
Add tomato paste, garlic, ginger and spice mixture and cook until fragrant, 2-3 minutes.
Add potatoes, water, vinegar, brown sugar and a pinch of salt. Bring to a boil, reduce heat and let simmer 20-25 minutes, until the potatoes can be pierced with a fork easily. Remove lid and cook for an additional 5-10 minutes until the sauce has thickened.
Serve with greek yogurt, cilantro and mint if desired.