Undoing the Brussels sprouts:

Rinse and drain the sprouts. Working over a big bowl with a sharp paring knife, cut off (and discard) a 1/4-inch or so of the base of each sprout, freeing the outer leaves. Now stick the point of the knife into what’s left of the base and slice out the tiny core, in one cone-shaped piece — just as you would cut out the bigger core of a cabbage or cauliflower. This loosens the inner leaves. Discard the small core.  

Begin peeling off the outermost leaves: discard only wilted or blemished leaves; drop all the fresh dark green leaves, even thick ones, into the bowl. Keep peeling off the leaves until you reach the tiny ones that can’t be pulled apart. Cut this bundle in slivers and drop them into the bowl. When all are done you will have a large fluffy pile of leaves. 

Skillet Cook the Brussels sprouts:

Put the oil and the garlic in the skillet and set over medium heat. Let the garlic cook and caramelize lightly for 4 minutes or so, shaking the pan now and then.

Dump in the sprout leaves, shake the pan to spread them out, and then sprinkle the salt and peperoncino all over.

Cover the skillet and let the leaves cook and wilt for 4 to 5 minutes, giving the pan an occasional shake, then uncover and turn them well with a big spoon or tongs. The leaves should be sizzling but not browning — lower the heat if necessary. Cover again.

Cook another 4 to 5 minutes until the leaves are soft, greatly reduced in volume but still green and glistening. Serve the Brussels sprouts hot right from the skillet or turn them onto a warm platter.     

To serve with lemon or another sauce, spread a 1/2 cup of warm sauce in the bottom of a platter and pile the Brussels sprouts on top. Scoop up sauce with each serving spoonful of leaves.