THOUGH I’VE BEEN A LIFELONG FAN OF BLUEBERRY jam, it was only very recently that I took a stab at making blueberry butter. The result is just wonderful: Less sweet and sticky than a traditional jam, it ends up tasting like blueberry pie in a jar.
8 cups puréed blueberries (about 3 dry quarts/1.7 kg blueberries)
2 cups/400 g granulated sugar
Zest and juice of 1 lemon
2 teaspoons ground cinnamon
½ teaspoon freshly grated nutmeg
Put the puréed blueberries in a 4-quart capacity slow cooker. Cover and turn it to low. After it has cooked for 1 hour, remove the lid and stir. From this point forward, you will want keep the lid slightly cracked. Propping it open with a wooden spoon or chopstick allows for the evaporating steam to escape.
This butter will need between 4 to 8 hours total in the slow cooker. The time varies depending on how hot your slow cooker cooks. Check the butter at least once an hour to track the progress.
In the final hour, add the sugar, lemon zest and juice, and spices. If you want to speed the evaporation, remove the lid and turn the cooker up to high. If you do this, make sure to check and stir the butter every 10 minutes to prevent scorching.
When the butter is nearing completion, Prepare a boiling water bath and 4 regular-mouth 1-pint/500 ml jars according to the process on page 10. Place the lids in a small saucepan, cover them with water, and simmer over very low heat.
Once it is as thick as ketchup and spreadable, determine whether you like a chunky or smooth butter. Purée the butter for a smoother texture; for a slight chunkiness, leave it as it is.
Turn the slow cooker off and ladle the butter into the prepared jars. Wipe the rims, apply the lids and rings, and process in a boiling water bath for 10 minutes (see page 11).
The sealed jars can be stored in a cool, dry place for up to 6 months.
