Less confident/savvy mustard might splutter rather than pop.

Method
1 Heat the vegetable oil in the pressure cooker. Add all the ingredients for the spice blend and fry until they start to splutter and smell aromatic.
http://www.reveal.co.uk/lifestyle/blog/food-recipes/?page=2

Method:
1. Heat oil in a pan.
2. Fry the mustard seeds till it starts to splutter.
3. Add the small onions and curry leaves.
http://www.awesomecuisine.com/recipes/6904/stir-fried-coloca...


Also 'crackle'

Heat oil in a medium skillet over medium heat, and cook mustard seed until it begins to crackle.
http://farmhousetable.wordpress.com/recipes/vegetarian-main-...



And here's an option that drives home the point about not scorching:

In a small skillet heat 40g butter and sauté the poppy seed until it begins to scent.
http://mobile.cooksunited.co.uk/recipes/m674911307516994/Pot...




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Note added at 11 días (2012-11-26 23:44:19 GMT) Post-grading
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or, as suggested, 'sputter'; e.g.,

In a wok, heat a couple of table spoons of oil. Once hot, season it with the mustard, urad dal, cinnamon stick and clove. Once the mustard sputters, fry the onion until soft.
http://iaminlovewithfood.blogspot.com.br/