Bengali Aachar Moshla is a different spice blend than North Indian Aachari Spices. We don't use mustard seeds or mustard powder in the Bengali version of pickle spices. There are other variations available, but I follow the recipe my mother learned from the mother of my tuition teacher. For me, this blend works best. You can make your own mix depending on your preference, but there is no hard and fast rule while following my recipes.