Is it safe to boil or steam French frisée lettuce (as one would with spinach and chard)? Does cooking the lettuce this way make it poisonous or inedible?
Frisée lettuce (Cichorium endivia) is not actually a lettuce, as this link from Yuma County (Arizona) Cooperative Extension says, but a leafy green related to endive and chicory. It is sometimes called curly endive, French endive, or escarole. There are at least 18 varieties. Leaves are eaten raw in salads, boiled, steamed, sauteed, braised, or cooked in soups and stews.The mature plants are sometimes blanched before harvesting to reduce the bitter flavor. In Java, they are pickled in brine.
Source: Cornucopia II; A Source Book of Edible Plants, by S. Facciola, 1998, p. 190, 362-363.
Frisée (confusingly called French endive by some) is almost a miniature version of curly endive or perhaps is more like the inner portion or heart of that plant. The outer leaves of frisée are light green to yellow, and the yellowing continues inside and becomes white at the center with a lace-like pattern with a milder taste than that of curly endive.
Frisee: A great little lettuce that is part of the chicory family. It is lacy and pleasantly bitter. As the lettuce grows, each head is tied up so that the sun does not penetrate the center of the lettuce as it finishes growing. This process blanches the frisee since the plant needs the sun to develop its normal green leaves. The delicate white leaves are considered a delicacy and are the least bitter.
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