for the jarred sauces that are very thick I normally thin them down with equal parts malt and balsamic vinegar plus a little sugar.
I am going to make my own. I found several recipes on the internet, and it looks dead easy. One key point is most of them said to steep the chopped mint leaves in warm water, then drain off the water. I’m afraid that will lose a lot of the mint flavor. Instead, I’m going to experiment with heating up the vinegar, steep the mint in it, then use it in the sauce.
Here is one mint sauce recipe I found, with three ingredients: https://www.kitchensanctuary.com/homemade-mint-sauce/ It’s from a Lebanese woman, and Lebanese know lamb…and mint.
Good luck.
I occasionally drink apple cider vinegar diluted with water and sweetened with honey. It’s supposed to be a blood thinner and health tonic. I’ll have to try it with mint sometime.
You’d basically be having mint sekanjabin.
In fact, we’ve made ours in bulk for medieval markets with mint sauce rather than chopping oodles of mint leaves.
From my childhood, I recall chopping up mint (spearmint, not peppermint) leaves from the garden (hint: plant it in a solid container, or it’ll take over the garden), and just mixing it with vinegar and sugar.