I've been using a cold-process method to make syrups for several years. All it takes is some patience and a little muscle, and the flavor is much brighter and truer to the ingredients. Just chop up desired ingredients (rhubarb, berries, fennel--options are numerous!) and combine with your sweetener of choice (sugar, honey, etc.) in a ratio of 1:1. Muddle (a potato masher also works well) and let sit for 30-60 min, repeating muddling every 15-20 min. When a good amount of the juices have been extracted, strain through a sieve or cheesecloth. Transfers to a mason jar and shake the heck out of it to dissolve and remaining sugar granules.