Bitterness has been bred out of most supermarket produce, which is why properly bitter greens taste startling now. Chicory and dandelion are the two great bitter infusions of European practice, and roasted chicory root is the coffee substitute that Napoleon-era France ran on. Cultivated dandelion is a different plant from the lawn weed - bred for tenderness, harvested young, bitter without being punishing. If you have only had the wild kind, this is worth revisiting.