Separate them from the stalk, and cut off the part that connects the sprout to the head using a sharp knife. Separate the stalk from each sprout individually.
Soak the Brussels sprouts in cold water for about 30 to 40 minutes and add salt. Drain the Brussels sprouts and rinse thoroughly.
Heat water in a large pot until it reaches its boiling point. Once boiling, add Brussels sprouts to the water. The larger Brussels sprouts boil for 5 minutes, the medium ones for 4 minutes, and the smaller ones for 3 minutes.
Following the allotted time, remove Brussels spouts from your cooking pot and put them straight into the ice bath. This will halt the cooking process and will help the Brussels sprouts firm up. Let them stay in the ice bath until they cool off.
Drain the Brussels sprouts and place them on a kitchen towel to get rid of excess water and dry the sprouts completely.
Line the tray with parchment paper and place dried Brussels sprouts on it. Make sure there's enough distance between vegetables. Put the tray in the freezer for 1 hour.
Lastly, take the tray out of the freezer and place the frozen Brussels sprouts in a plastic zip-lock bag or container. Seal it tightly and store it in the freezer. The Brussels sprouts are good to last for about 12 months.
Notes
Blanching Methods: You can blanch Brussels sprouts through water or steam. Water blanching is typically the best for home freezing; steam blanching takes about 1.5 times longer.
Faster Freezing: Place the sheet of sprouts close to where cold air enters your freezer.