Clean the gooseberries by removing the tops and tails.
Place the cleaned gooseberries in a pot with the water and lemon juice. Bring to a boil over medium-high heat and cook until they disintegrate, about 5 minutes.
Stir in the sugar and boil hard until the jam reaches gel stage, about 8 to 10 minutes. Test on a frozen plate, check that it sheets off a spoon, or use a thermometer (220°F at sea level). Pull it the moment it gels, since gooseberries set hard if overcooked.
Pour the jam into prepared jars, leaving 1/4 inch headspace. Apply two-part lids finger tight.
Refrigerate for immediate use, or process in a water bath canner for 10 minutes for shelf-stable jars.
Notes
Fruit Amounts: Gooseberries run about 3 cups per pound. One pound of sugar is about 2 cups. A 1:1 fruit-to-sugar batch gives the firmest set. You can reduce the sugar to 3/4 pound per pound of fruit (that'd be 1 1/2 cups instead of 2), and it will still set at that point. Don't reduce it more than that to ensure set.Yield: One pound of gooseberries makes about 3 half-pint jars at a 1:1 sugar ratio. A reduced-sugar batch yields a little less.Sugar Amounts: Gooseberries are tart, and the sugar helps the jam set, so don't skimp. Use 3/4 to 1 pound of sugar per pound of fruit. A full pound sets firmest.Batch Size: You can double the recipe, but don't go past 2 pounds of gooseberries per batch. Larger batches heat unevenly and may not reach a good gel.Tops and Tails: Each berry holds a bit of stem and a dried tail that should be pinched off before cooking. No need to mash the berries, they break down on their own.Seedless Option: Cook the berries down and strain before adding the sugar for a smooth, seedless jam.Frozen Gooseberries: Cook straight from frozen, no need to thaw first.Sugar Substitutes: Monk fruit and other sugar-free sweeteners won't set. For a lower-sugar jam, use a no-sugar-added pectin made for the purpose.Altitude Adjustment: Process for 10 minutes below 6,000 feet, or 15 minutes above 6,000 feet. Gel stage also drops about 1 degree per 500 feet of elevation.