Hervé This-Benckard, also mentioned on this blog, combines the art of cooking and chemistry. I have here a German translation of his Les secrets de la casserole. Most enlightening is his explanation why green vegetables should be boiled in much, lively boiling, water and without a lid. Note: this recommendation is entirely the opposite of what <fill in favorite term> have told their daughters for centuries.
As it happens, while boiling, some of the vegetable’s cells burst and release organic acids the hydrogen ions of which want to supplant the magnesium atom in the center of the (green) chlorophyll molecules. The resulting phaeopythin (no personal acquaintance) reflects more than just green and thus everything starts looking like a muddy brown mess. An open lid and high temperature make that the larger part of these organic acids evaporate together with the steam, and hence the process of browning is delayed. (Hervé This-Benckard, Rätsel der Kochkunst [Piper: 2001] p. 122). Thank you, Hervé!
A whole nother problem is the matter of cooking vegetables evenly that want to cook unevenly by nature. In his otherwise absolutely delightful book Roast Chicken and Other Stories, Simon Hopkinson heaps scorn upon the “tall, very silly pan called an ‘aspargus pot,'” in which the water “is supposed to boil the parts of the asparagus in the water and steam the tips.” (p. 11f.)
These pots are expensive and might indeed be considered a “waste of money,” but it should be acknowledged that they do in fact boil the stems and steam the tips. Perhaps, with the green “British crop” of asparagus that Hopkinson prefers, the mushiness of the tips is no issue. With the white kind that is eaten in some other parts of the world, it is in fact a true worry. I never got around buying an asparagus pan and am using my oval cast-iron pan instead. It works fine for boiling asparagus (or spagetti), but trying to retrieve the stems without breaking off the tips is really quite agonizing.
A more day-to-day vegetable that confronts us with the problem of premature decomposition of part of its structure is broccoli. The stems, which – if properly peeled – are absolutely delicious, cook at least five minutes slower than the florets. So what we get, when boiling this vegetable according to Hervé or Simon, is either fantastically green broccoli phantoms that partly crumble into a (still green) mush when we barely look at them, or beautifully buttery florets with still creaky stems. Either is undesirable and has probably contributed to the bad reputation of this most noble one of the simple vegetables.
Fortunately, broccoli’s sheer bulk helps us to create an asparagus-pot-like situation in the pan, which solves the whole problem. For this it is, I repeat, absolutely necessary to carefully peel the stems. Then the broccoli is divided into portions, by halving, or even quartering, the stems from below and cutting upwards into and through the top. The resulting sections are arranged, floret up, in a pan in which the salted water has started to bubble vigorously. About 2 to 3 inches of the brocco-tops should emerge from the water. Boil until the thickest parts of the stems are just tender.
Now, of course, comes the real fun. The retrieved Broccoli can be sauteed in olive oil with parsley, pepper and garlic, soaked in molten butter, treated with lemon juice and olive oil or combined with grated cheese and béchamel sauce, for example