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The saucepan should be large enough to hold 2.5–3 US qt (2.4–2.8 L) of liquid. Though you won’t be adding nearly that amount of water, this size of saucepan will be plenty large enough for 1 lb (450 g) of chopped broccoli.  3  fl oz (89 ml) also equals 6 Tbsp. Adding more water than this small amount will only cause the broccoli to boil. You need just enough water to create steam. Choose a saucepan with a lid that fits snugly. If necessary, you can use a heat-resistant dinner plate as a lid. Do not remove the lid to check the broccoli—you need to keep the steam trapped inside. This trapped steam  will continue to cook the broccoli without overcooking it.

Summary:
Add 3  fl oz (89 ml) of water to a medium saucepan. Reduce the heat to low and steam the broccoli for 3 more minutes.