Besides Plum Pudding at Christmas, the only thing I know for certain was a recipe used by my English/New Zealander grandmother Elizabeth Pressland Fletcher is this one, for Mint Sauce. I can hardly eat lamb chops without it. And don't even mention Mint Jelly! My mother had a special little face and an emphatic "Yeeech" for that.
Take those leaves and put them in a glass bowl or sauce pitcher. If it's not heat resistant, leave a metal spoon in it to absorb some of the heat when you add boiling water.
Add a good amount of sugar, then
half of that amount of salt.
Then cover your mint with boiling hot water and stir. Let it steep for about 10 minutes.
After it has steeped 10 minutes, add three or four tablespoons of vinegar. I have used white, apple cider, and balsamic vinegar. I think I like the apple cider the best, but it's all good.