Green Chartreuse is a famously intense herbal liqueur made by Carthusian monks from a large blend of botanicals. It’s high-proof for a liqueur and tastes like concentrated alpine herbs, mint, anise, peppery green spice, and sweetness.
It behaves like both a sweetener and a complex “herbal engine” in cocktails. Small amounts can dominate; the magic is how it adds bright green aromatics and a long, layered finish.