Remove leaves from stems. (Swiss chard stems are edible, so save and cook them) Blanch greens in a large pot of boiling salted water, 15 seconds (spinach and chard) to 2 minutes (kale and collards); drain. When cool enough to handle, squeeze out excess liquid; let cool completely in a single layer on a rimmed baking sheet. Greens can be stored in an airtight container in refrigerator up to 4 days.
Cook's Notes
Cooked-Greens Yields
That bundle of fresh greens may look enormous—until it cooks down. If you need a particular amount, weigh it in the store, or play it safe and buy two bunches.
1 lb. collards = 2 cups
1 lb. kale = 2 cups
1 1/2 lb. spinach = 1 1/2 cups
1 lb. Swiss chard = 2 cups
