Add blackberries and honey to small pan, and simmer over low heat until blackberries have cooked and fall apart when stirred.
Put the mixture through a food mill or sieve to remove seeds. You'll end up with right about a cup of thick liquid once the seeds are removed.
Add water kefir, gelatin, and probiotic powder, and blend well with an immersion blender or whisk. If you're using a whisk, it works best to sprinkle the gelatin in slowly as you continually mix. If you're using the immersion blender, you can just dump it all in and blend.
Once the mixture is smooth and well blended, pour it into the cavities of your silicone gummi mold. I find that transferring portions of the mixture to a small measuring cup with a spout makes it easy to fill those tiny gummi bear cavities without making a mess! Some folks recommend using an eye dropper to make this part easier.
Allow the mixture to cool. They'll set just fine at room temperature, but putting them in the fridge or freezer for about 15 minutes speeds things up! I also find that the colder and firmer they are, the more easily they come out of the mold.
Store refrigerated, in an air-tight container.