I feel ya on this one. I love the taste of blackberries, but I can’t stand all those little seeds. While you can remove the seeds during prep, the process will break down the berries. You’ll end up with juice and berry pulp instead of whole berries. For this reason, I tend to skip removing the seeds, but if you’re adamant, here’s how to do it. My go-to method is to use a food mill. A food mill is a hand crank device used for straining and pureeing foods. You fit the food mill with one of three perforated blades. As you crank the food mill, it presses the food against the blades. The perforations on each blade are smaller than the next. The finer the blade, the more that’s extracted from the food. You will likely need to pulse the berries in a blender or food processor first to break them down a bit. Then run them through the mill. The blade with the largest holes will remove the skins, the second largest will extract most of the seeds. The smallest will remove all of the seeds but you will be left with mostly juice. The second method is to use a mesh sieve or colander. Pulse the berries as mentioned above. Transfer them to the colander fitted over a large bowl. You may need to use the back of a spoon to extract as much juice from the blackberries as possible.