Have you checked out all the recipes in the discussion linked below?

What books do you have available? I know both Ferber's books have some good recipes in them.

This recipe is from Food in Jars

Seedless Blackberry Jam

6 cups blackberry pulp (8-9 cups of berries, mashed through a strainer with the back of a wooden spoon)
4 cups sugar
2 teaspoons cinnamon
1 teaspoon freshly grated nutmeg
1 lemon, juiced and zested
1 packet liquid pectin (half the box)

Standard instructions but don't forget that once the pectin is added a good hard boil for 5 to 7 minutes to insure set is needed so watch out for scorching.

And be sure to freeze some of the blackberries so you can make Blackberry-Peach jam once the peaches come in.

Dave

Here is a link that might be useful: Fancy Strawberry jams

I do know from personal experience (and not following directions) that if you use a blackberry jam/jelly recipe that calls for 3 oz liquid pectin and use artificial sweetener instead of sugar, it will make blackberry sauce that never will set up - but is delicious on ice cream and/or cake, added to lemonade, as a sauce on pork or chicken. I'm sure the same would work for strawberry.

As our family has grown older we use less Jam, but use more "syrup". There are multiple sources for blackberry/XXXX jam recipes available with a google search. To make the syrup we just back off of the pectin.

This may not fit your request, but here is a recipe for Blackberry/Peach Jam.

Here is a link that might be useful: jam

i just canned a great experimental batch today: a "low sugar" strawberry jam with balsamic vinegar, black pepper, and cardamom. the cardamom was a variation on the wider-used balsamic/pepper recipe.

I basically made the recipe on the package of the Sure Jell Low Sugar pectin box, but with the following variations:

*mixed the fruit and sugar (half white/half brown) and let it macerate overnight

*strained and brought the syrup to a boil, then let the fruit sit in the boiled syrup most of the day

*then proceeded with the process on the Sure Jell box: added pectin, brought to full rolling boil for 1 min

*I added 4 tbs balsamic vinegar, about 1/2 tsp fresh ground pepper, and 2 tbs cardamom to the mixture while it boiled

then canned in a water bath like normal.

turned out super tasty!

Well, first try mixing the two. Will thin out the seedy blackberries. Unless you can run them through a food mill. I make cherry raspberry so I imagine cherry blackberry might be good too. I just love the blackberry though, but I hate the seeds! Blackberry plum sounds interesting, or blackberry blueberry. Before I had a food mill I would always mix my seedy berries with unseeded stuff.

Dave's link to the Fancy Strawberry Jams is a good one. I made Christine Ferber's strawberry, mint, and black pepper preserves for the first time this year and it is superb, though if you've not made jam without pectin before there is a bit of a learning curve, especially with strawberries. My first batch turned out a bit too taffy-like from cooking for too long. The second batch was an improvement and I believe worthy of gift-giving...a bit more syrupy but all the better to spread on toast, waffles, or what-have- you. The strawberry, balsamic, black pepper version is also good, though the balsamic is very subtle.

Epicurious:

Strawberry Jam With Black Pepper, Ginger, And Bay

2 kg hulled and quartered strawberries
400 grams organic brown sugar
400 grams organic granulated sugar
2 pieces, pith-free lemon zest
3 tablespoons lemon juice, from the above lemon
1 bay leaf
1 tablespoon freshly ground tellicherry black pepper
2 tablespoons peeled and minced fresh ginger

Place a heavy pot (I use a big old cast iron enamel pot) over medium high heat and add the strawberries. Cook for five minutes and then add the sugars. Stir well and cook for five more minutes. Add the zest, the lemon juice, the bay leaf, pepper, and ginger. Cook for about 45 minutes, stirring often. Check for consistency and temperature.

The jam should be boiling, and when it gets to 220 degrees F keep an eye on it. Test with the cold plate for consistency and remove from heat when the desired consistency is met. Place in jars with 1/2 inch of headroom, cap and process in rapidly boiling water for 30 minutes. Remove jars to a cooling rack and when they have cooled, label them and store them in a cool pantry.

Make a marmalade with the strawberries or blackberries as the base. When I was a kid, my mom made a fig marmalade that was awesome, and I've done the same when I had lots of peaches or other fruits.