When the pan is very hot, add the chicken in a single layer, using two pans or cooking in batches if necessary. (acalculatedwhisk.com)
Don't bother cooking it in batches of one layer, just toss it all in your pan if there's not room and stir it up as more fat renders. (thewickednoodle.com)
Continue to cook in batches until the onions are all cooked. (angelaskitchen.com)