My apologies for a lack of link, although hopefully my description will suffice. I saw some transient video of chefs making Bananas Foster in, I believe, New Orleans. They were shaking a powder into the flames to produce a dramatic sparks effect. What is this powder? I can't find any YouTube videos of it, so I believe it might be a lesser-known, regional flourish. At any rate, it looked spectacular and I would recommend it to anyone flambé-ing in front of an audience.