I rely exclusively on Fuchsia Dunlop’s books for cooking Chinese food. Sometimes her British background gets in the way, as ingredients she calls for can be hard or impossible to find in San Francisco. Most recently, I wanted to use “ya cai” 芽菜 to make dan dan noodles but had to settle for Tianjin preserved vegetable 天津冬菜, despite inquiries at several Irving Street emporiums. Dunlop casts aspersions on the Sichuan peppercorns typically for sale in the USA. Has anyone noticed much variation, and if so please direct me to the very finest “hua jiao” 花椒.