1. Wash and peel potatoes and cut them into 1/2-inch pieces. Place in a medium saucepan, cover with cold water, and bring to a boil over medium-high heat. Lower heat to medium and cook until potatoes are just tender, about 6 minutes. Drain and set aside to cool to room temperature, about 30 minutes.
2. While potatoes are cooking, heat oil in a medium skillet over medium-low heat. Add jalapeño and cook until slightly softened, 1 to 2 minutes. Add mustard and cumin seeds and cook, stirring, 1 to 2 more minutes, until the mustard seeds start to pop. Add turmeric and cashews and continue cooking, stirring frequently, another 2 to 3 minutes. Set mixture aside.
3. When potatoes have cooled, place them in a large serving bowl. Add the cashew spice mixture, mint, cilantro, yogurt, and salt. Stir gently to combine. Serve at room temperature or chilled, garnished with mint or cilantro sprigs if desired.
Source: fresh magazine May, June 2010