Shaanxi chili oil, made by pouring very hot oil over ground chili, often with sesame seeds; Shaanxi cooks add a little black vinegar at the end. It seasons 凉皮 and is also eaten with rice.
Mixed noodles absolutely need a spoonful of chili oil.
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culture
Made by pouring smoking-hot oil (often with Sichuan peppercorn, sesame, five-spice) over coarse chili flakes to bloom their aroma. A local saying places it among Shaanxi's 'Ten Strange Things' (陕西十大怪): 油泼辣子一道菜 - 'chili oil is a dish.'