Mustard seeds are widely used in Indian cooking, although the black/brown ones prevail. No reason why you can't use the yellow, though. Try something simple:
Parboil some whole green beans. Drain and set aside.
Heat some oil ( or ghee) in a pan, and when hot, add a tbsp of whole mustard seeds. When they begin to pop, add a tsp of minced garlic, and two tbsps grated coconut, stir around once or twice, then add the beans. Stirfry until just tender. Salt and pepper to taste.
I always use mustard seeds in my pickling spices, too.