While reading through a previous post, I heard someone suggest pairing balsamic vinegar with strawberries in a dessert, but first reducing it with a pinch of black pepper and some sugar. I've tried it twice, and love the flavor combination! However, I can't seem to get it to "reduce" - it simmers along and mixes, but no matter how long I leave it on for (and this is on low heat) it never thickens at all. Am I expecting something unreasonable? Any tricks of the trade that I'm missing out on?