Our buff orpington went broody (rather early to go broody-- she's only been laying for about 3 months, and she's from a fairly common breed, when broodiness is not as common). So, after a few weeks of this (you have to allow enough time for her to think she's sat on eggs long enough to produce chicks), I snuck out in the darkness last night and stuffed four, barely-day-old chicks under her.
She fluffed up immediately for them to curl under her feathers. I took that as a great sign, and crossed my fingers for all chicks to be alive and happy come morning.
Puffed up and EXTREMELY protective. Hurray for this and hurray for not having to worry about raising four chickies!