If you want to keep the fiery taste of the mustard, add the seeds towards the end of the cooking process, but if you want something smoother, try following Southern Indian tradition by gently frying the seeds in butter. This gives the seeds a completely different nutty taste.
To make a deliciously simple chicken curry, fry the seeds in a little butter and mix with turmeric and some chilli powder before adding chicken and a little water; simmer until cooked. Take care when toasting or frying mustard seeds as the seeds will jump around the kitchen as they pop, so have a pan lid handy. They will turn bitter if they are allowed to burn so once they start to pop take them off the heat to blend in your other ingredients. Reference to the humble Mustard Seed appears in all major religions, demonstrating the importance and ubiquitous use of this spice.