Watch out when you dive into this curry, because hidden among those greens beans are hot chiles, sliced the same way as the beans. The rice flour, in addition to thickening the sauce, mellows out the chiles’ pungency with its starchy presence.
Heat the oil in a large skillet over medium-high heat. Add the mustard seeds, cover the skillet, and cook until the seeds have stopped popping (not unlike popcorn), about 30 seconds. Add the lentils and stir-fry until they turn golden brown, 15 to 20 seconds. Immediately add the onion, chiles, ground mustard, fenugreek seeds, and turmeric. Stir-fry until the spices are frag