Hmmm. Well, I've never managed to get sweetener to caramelise, but there is this stuff called Inulin. I've got some but haven't used it yet. There is a recipe in Tom Kerridge's Dopamine Diet book where he makes a creme caramel & uses Inulin to caramelise the top with a blowtorch. So by this assumption, Inulin should caramelise. It is very low GI so shouldn't affect BG's much (in theory) & I don't know how sweet it is so not sure how much you should use. It's available online.