This classic British springtime jam is a composite of two recipes: one from Bon Appétit, and another from a family friend who was born and raised in England.

Steps

1. Place the chopped rhubarb in a large bowl and toss with 1 cup of the sugar. Let sit overnight.
2. The next day, rub the inside of a large, heavy-bottomed pot with a bit of butter. Put the macerated rhubarb into the pot and, stirring frequently, bring the mixture to a boil. Turn the heat down to medium and, still stirring frequently, cook until the rhubarb has softened. Add the remaining 2 cups sugar, the crystallized or candied ginger, the ground ginger, the lemon juice, and the zest, if using. Simmer on medium-low heat, stirring occasionally, until the jam is mushy and thick, about 20 to 30 minutes.
3. Meanwhile, bring a large stockpot of water to a boil, with a cake-cooling rack inside for the jars to sit on. Put 6 half-pint jars on the rack in the pot to sterilize. Soak the lids, ring bands, and canning tools (tongs, spoon, and the like) in a bowl of hot water.
4. To see if the jam is ready to can, put a teaspoon of jam on a saucer and give it a minute or so to cool. If the jam forms a skin and isn’t too runny, then it’s ready to be canned. When the jam is done cooking, add the vanilla extract if you wish.
5. Once the jars have boiled for at least 10 minutes, use the canning tongs to remove the jars from the water. Spoon the hot jam into the jars, wipe the rims clean with a damp clean cloth, place the lids on the jars, and screw on the ring bands. Submerge the jars in the stockpot’s hot water and simmer for at least 10 minutes. Remove the jars from the stockpot and set them on a dishtowel, at least 1 inch apart. Let cool on a dishtowel for several hours. (The lids will pop as they seal while cooling.) Store in a cool, dark place.