To check if your meringue is stiff, lift the beaters out of the bowl and upend them: The peaks should stick straight up.
Our taster's couldn't stop eating these! Can't find finely shredded Cheddar? Buy a chunk of Cheddar and shred it against the small holes of a box grater---the fine shreds cling better to the chicken.
Make sure to get your whisk into the bottom edge of the pan as you prepare the custard so that the mixture cooks evenly.