BURNT ONION SKINS | I like to use vegetable ash in my cooking. This photo is a detail of burnt red onion skins + banana shallot skins after one minute in the hot oven. I love watching the change in colour and textures when the onion skins curl up, wrinkle and slowly turn into ash. Vegetable ash adds smokiness to your dish. Try making ash with members of the allium family such as onions, leeks and garlic. Using the skins to make ash is an easy way to prevent food waste.