Bring a large pot of water to a boil. Alternatively, you can use a vegetable steamer basket over a couple inches of boiling water.
Cut the broccoli into florets of similar size. Wash under cold running water, and pat dry. Fill a large mixing bowl with ice water.
Once the water is boiling, drop the broccoli into the pot and cook for 3 minutes. If using a steamer basket, cook for 5 minutes. Do not overcook the broccoli. It should turn bright green but still be fairly firm and just gently cooked.
Immediately transfer the broccoli to the bowl of ice water. You can use a slotted spoon to do this quickly or drain the broccoli first then transfer it.
Let the broccoli sit in the water for a few minutes before transferring the florets to clean paper towels or dish towels. Use a slotted or strainer spoon if you have one.
Pat the broccoli as dry as possible. I often will squeeze the florets gently in my fists to ring out any excess water.
Spread the blanched and dried florets out on a baking sheet in a single layer. Place the baking sheet in the freezer, somewhere it won't get bumped, and freeze for 1 to 2 hours until frozen solid.
Transfer the frozen broccoli florets to a freezer bag. Seal tightly, removing as much air as possible.
Label and store in the freezer for up to 6 months. Use within 3 months for best results.
Add directly to cooked dishes without thawing first. Do not use it in raw broccoli salads or else it will be mushy. I also recommend steaming instead of boiling if you are using it for a simple side dish.
To freeze broccoli without blanching, just cut it up and store in a freezer bag. Remove as much air as possible. Freeze and use within 1 month for best results.