Please choose the correct ending to complete the given sentence: Food and Entertaining: [header] How to make french onion soup casserole [title] Slice the onions and the celery. [step] Cut off the very top and bottom of the onion and then cut the onion in half on the vertical. Discard the cut off portions and the papery outer layer.

Ending1: All you need now is a well-rounded onion (preferably one that's been charred and roasted). You need to thinly slice the onion and the celery slices; any excess won't work as a substitute. Ending2: Then use a fork or a knife to slice the onions into thin slices. [substeps] Since french onion is so sweet, it can go well with a variety of sauces and stews. Ending3: Then place both onion halves flat side down. Cut vertically to create thin slices through each onion half. Ending4: Take the cut onion and peel the onion into small chunks and then halve the skin off the onion. Cut each cut into fourths and then halve the halves into quarters.

Answer format: ending1/ending2/ending3/ending4