As many of you probably agree, strawberry jam is often cloying, too sweet to be enjoyed. In large part this is because strawberries have little in the way of natural pectin so you really have to add a lot of sugar to compensate. As well, cooking strawberries seems to concentrate their natural sweetness, adding to the sugary taste factor. I tend to avoid adding pectin because the liquid and powder synthetic forms leave a slightly metallic aftertaste and/or an unnatural wobble. Pomona's works well but can be a bit high maintenance, and I never seem to have calcium water readied or the calcium packet within reach.
To avoid pectin altogether while jamming with a fruit that really needs it, I use one grated apple per 4 cups of berries and cook things until reduced and thick. What results is a beautiful, richly colored somewhat loosely set preserve whose sweetness is perfectly offset by lemon juice, cardamom and the slight tang of the apple.
You can double this recipe, just make sure you ready the appropriate number of jars and use a pot large enough to provide good surface area for the jam as it cooks. —em-i-lis
washed and trimmed strawberries (preferably organic), cut into halves or quarters
unrefined, granulated sugar
juice of 1/2 lemon
ground cardamom; use a nice pungent one; I like Guatemalan
small apple (roughly 4 ounces), peeled, cored, grated
Fill your canning pot with water, cover, and set over high heat. Do this first because it takes a long time to bring this much water to a rolling boil. Ready the appropriate number of jars and get out your canning funnel, ladle and such.
In a jamming pot or other heavy-bottomed stainless pot, stir together all your ingredients. Let sit for a half hour (you can also macerate this overnight; in that instance, don't start heating your canning pot until you're ready to actually cook the jam).
When a decent amount of syrup has pooled around the strawberries, set the pot over high heat, and stir regularly (but not constantly) as the mixture comes to a boil. You want it to boil like crazy so as to evaporate as much water as possible.
Strawberries foam a lot so if that bothers you visually, skim or carefully spoon the foam off. Keep stirring, and if your berries aren't breaking down as you'd like, crush them with a potato masher. It really depends on how much "chunk" you like in your jam.
If you've not already, sterilize your jars by placing them in the boiling water bath. Sterilize your lids too either by putting them in your canning pot for 2-3 minutes as it boils or by placing them in a smaller pot of boiling water which you then remove from heat.
If you have a Thermapen or similar instant-read thermometer, start checking the temp after about 20 minutes. You want to get to at least 217° F. When things are getting close, a rim of strawberry gunk should have adhered to the sides of your pot (at the level of the jam), the bubbles should look thick like lava, not loose like boiling water, and the jam should sheet not rain off the back of a wooden spoon.
When the jam is ready, carefully ladle it into your prepared jars, wipe the rims, apply lids and bands, and carefully place into your canning pot. Process for 10 - 12 minutes, remove and sit on a kitchen towel for at least two hours.