Concord Grape Jam

Ingredients

• 8 cups Concord grapes
• 6 cups granulated sugar
• Juice of half a lemon
• 1/2 teaspoon unsalted butter

Directions

1. If you plan to can the jam, get the jars and lids ready first: set 6 half-pint jars on a rack inside a large pot. Pour in enough water to submerge the jars, then bring it to a boil over high heat. Let them boil for 10 minutes, switch off the heat, and leave the jars sitting in the hot water. While that happens, set the bands and lids in a small saucepan and add water to cover. Warm them over medium heat until the water reaches a simmer, then take the pan off the heat and keep the bands and lids in the hot water until you need them.
2. Now pinch each grape with your fingers so the skins slip away from the pulp. Put the skins in a food processor and pulse until they are roughly chopped. Scrape them into a large heavy-bottomed pot and pour in 1/4 cup of water. Bring the pot to a gentle simmer and cook until the skins have softened a little, about 10 minutes.
3. At the same time, add the grape pulp to a medium saucepan and bring it up to a boil. Lower the heat and let it simmer until the grapes collapse and no longer hold their shape, about 10 minutes. Set a fine mesh sieve over a large bowl and pour the pulp through it. Press out as much pulp as possible, then throw away the seeds.
4. Stir the strained pulp into the pot of grape skins. Add the sugar, butter, and lemon juice, then bring everything to a boil while you stir constantly. Turn the heat down and keep it at a simmer, stirring often, until the jam cooks down, thickens, and reaches the gel stage, about 45 minutes. For the set check, put a small plate in the freezer. Once the plate is cold, add a small spoonful of jam and place it back in the freezer for 1 minute. Run your fingertip through the jam, then tip the plate from side to side. If the line holds and the jam does not flow back, it is ready; if it runs, simmer the jam for a few minutes more.
5. Use a ladle to fill the hot sterilized jars with jam, leaving 1/4-inch headspace. Wipe the jar rims clean, set the lids in place, and turn the bands on only until they feel barely snug. Set the jars on the rack in the pot and add water so they are fully submerged. Cover the pot and heat on high until the water boils. Boil for 10 minutes. Shut off the heat, remove the cover, and let the jars stand in the water for 5 minutes. Lift the jars out of the pot and let them sit undisturbed on the countertop for 6 hours or overnight.