If you love blueberry jam, you will adore blueberry butter. Use it on top of oatmeal, between layers of buttermilk cake, or with lemon curd on individual Pavlovas. Please read How to Process.

Puree in batches in a food processor:

Transfer the puree to a heavy pot or roasting pan and add:

Bring to a boil and simmer, stirring frequently, over medium-low heat or bake in a 300°F oven, stirring every hour, until the butter is thick and can be mounded on a spoon, 2 ½ to 3 hours on the stovetop or 3 to 3 ½ hours in the oven. It should not exude any thin liquid.

While the butter cooks, prepare a water-bath canner, gather all your canning equipment, and have ready 4 clean, hot half-pint jars. Ladle the butter into prepared jars, leaving ½ inch headspace. Wipe the rims. Place lids on jars and screw on rings until fingertip-tight. Process for 15 minutes. Let cool completely and store as directed.