Green Mangoes with a Yogurt-Toasted Coconut Sauce

My sister-in-law, Geeta, has a passion for food. If you need to know where to go for the best samosas or the sweetest mangoes, she can rattle off the appropriate vendors. Her cooking reflects her enthusiastic culinary meanderings, and this curry with unripe mangoes also mirrors her familial heritage as a Palghat Iyer from Kerala. Kalan is also made with winter melon, but I find this version far more interesting.