Blueberries from Slow-Cooker to Jar

I see dozens of recipes online every week. Some I glance at; others I don’t. A few, however, make an impression, like this one for Slow-Cooker Blueberry Butter. Printed sometime in July on Saveur magazine’s online site, this recipe hails from food blogger Marisa McClellan’s recently released book on home preserving, Food in Jars. This recipe, I wanted to try. Why? Take one underused slow cooker and an unfamiliar method for making jam. Add to these a pinch of serendipity (I actually had exactly 1.7 kilograms of blueberries tucked away in the freezer) and I have in front of me a recipe that indulges both my love of experimenting and my taste for summer fruit preserves.

And I do love fruit butters. These are spreadable and buttery in texture, less chunky than jams because they are made with completely pureed fruit, and not at all wiggly like jellies because they contain no added jelling agents. Fruit butters usually use less sugar than either jam or jelly, in my opinion allowing the fruit’s flavor to shine. Apple butter may be the best known here in the US, but late fall’s pumpkin butter continues to gain fans for its spicy pumpkin pie creaminess. However, it’s the Eastern Europeans who really embrace fruit butters: cooking down fresh and dried stone fruits and making prune, apricot, and plum butters out of them for years, spreading these on toast or baking them into pastries and cookies.

I returned to the bookmarked recipe just as summer’s weather veered into fall’s breezy days, chilly nights. Cooler is the perfect preserving weather, and throughout the summer I will stockpile my favorite fruits and berries in the freezer while I wait for this exact moment. In theory, one could just as easily make the above recipe in July with fresh, just-picked berries, for the slow-cooker won’t heat up your kitchen like a big stockpot set over a gas flame might. Ladle the preserves into clean jars and the fruit will keep for up to 3 weeks in the fridge. These can also be frozen for up to a year.

But because I like to give the filled jars the water bath canning treatment to extend shelf life, I know I will have to turn on those flames under the canning kettle and heat up the mid-summer kitchen anyway. So I freeze and wait out the heat instead. My method works for me; it might work for you too.

Making the preserves in a crockpot takes longer than making them on the rangetop, of course, but a cook might start this mixture simmering in the morning and finish the job after a workday. The blueberry butter might be made overnight too. Either way, the results are great, and perfect for those of us who want homemade preserves but have no time to stand over a pot, stirring. If you’ve been looking for a preserving process that would accommodate you, there’s no better place to start than with this Slow-Cooker Blueberry Butter.

Take a look at how I did making my own batch:

After thawing the berries overnight in the fridge, they made a nice puree

Puree in the slow-cooker, the lid partially open at one end

Darker and thickened and ready for the sugar, lemon, and spices

Almost all the hot blueberry butter has been ladled

Filled jars wait for the screw rings and the hot water bath

Time to clean up

Six half-pints successfully sealed and cooling

If the slow-cooker preserving appeals to you, I can suggest a few other recipes to try. I might be making this recipe for Polish Plum Butter next, with the Damson plums I have in the freezer. Take advantage of the brief Italian prune plum season this September and make your own batch.

Or, if you’d like something a little more unusual, here’s a tasty recipe from Martha Stewart for Bacon Jam, not a fruit butter but delicious and worthy of bringing the crockpot out of storage.

My friend and fellow blogger, Tammy McLeod, also had her slow-cooker out this week for making a large batch of caramelized onions, and she writes about both her bounty of onions and the resulting caramelized onions she made from them on Agrigirl’s Blog. I’m going to take Tammy’s unctuous onions one step further. After you’ve made your own batch using Tammy’s instructions as your guide, turn some of the caramelized onions into Onion Jam. This recipe comes from America’s Test Kitchen Slow Cooker Revolution as a suggested use for slow-cooker caramelized onions.

Caramelized Onion Jam

Pulse 1 cup caramelized onions, 2 Tbsp. dark rum, 1 Tbsp. brown sugar, 1 tsp. minced fresh thyme, and 1/2 tsp. cider vinegar in food processor to jamlike consistency, about 5 pulses. Season with salt and pepper to taste. Makes 1 cup. Spread on sandwiches or serve with cheese. (This jam can be refrigerated in an airtight container for up to 7 days.)

©2012  Jane A. Ward