In a 10- to 12-inch frying pan over medium-high heat, combine oil, caraway seed, and cumin seed. Stir until seed smells slightly toasted, about 2 minutes.
Add onion, garlic, serranos, and ginger; stir until onion is limp but not browned, about 2 minutes. Stir in turmeric and potatoes, then add cayenne to taste. Stir often until potatoes are hot, about 2 minutes.
Add cilantro, mint, and lime juice. Mix, then add salt to taste.