Don't use expensive balsamic vinegar for this one. Since you're cooking it down, the nuances that make the pricey kind worth it will cook away, so there's really no point.

The really beautiful thing about this recipe (besides how inexpensive it is, how few ingredients it requires and how breathtakingly gorgeous it looks when you plate it with a little kale salad and some fresh strawberries) is how impressed people are by it when you put it in front of them. You get to use fancy words like "reduction" and "macerated" when you describe how you made it, leaving your dining companion to ooh and ahh and think sexy thoughts about you (unless, of course, you don't want them to, in which case they'll just think about how smart and competent you are). 

A few pointers: Firstly, this is a great way to use up strawberries that are a day or two away from being too mushy to eat. Just slice 'em up and let them cook down into sweet, syrupy deliciousness. And speaking of which, if you want to skip adding the sugar when you make the sauce, that's just fine. The sauce will be a little bit more tart, but the sweetness from the balsamic and the strawberries will still keep it in the right ballpark. 

Secondly, don't use expensive balsamic vinegar for this one. Since you're cooking it down, the nuances that make the pricey kind worth it will cook away, so there's really no point.

Finally, if you want use chicken breasts instead of thighs, go right ahead. Personally, I prefer the deeper flavor, higher level of juiciness and lower price of the leg-thigh cut.