I travel to Brussels every now and then and frequent a restaurant called The Belga Queen. They usually have a dish with this apple and pear syrup...over meatballs served in a cast iron pot. I once had it over what was presented as a little piggy too.
For the life of me I can't find a recipe on how to make this syrup, and any info that I DO find usually mentions something about it being super-top-secret-only to a certain region of Belgium. From my translations and research it seems father difficult to make.
There is a (non-us) company that makes in a jar, but I don't feel like mail ordering and paying out of the nose for this.
I'm not sure the rules on posting links, but if you google it, you'll see what I mean.