I'm not talking about the one caused by grease, but the one that occurs spontaneously. A little puff that sends thousands of sparks around.
I would call it "crackling"...
Wow... No two dictionaries have the same definitions for this, but you could use flare, or flare-up or "sudden flare". (Or, "little explosion")
There is quite a bit of scope here for using onomatopoeic words like snap, bang, pop, crack and the like, particularly if you double up the descriptive verbs to make the intended meaning clear:
The bonfire sparked and popped, and the damp logs that lay uppermost began to steam.