From Great British Cooking by Jane Garmey.
In our house, lamb is not complete without mint sauce. This recipe makes about 3/4 cup. If made with vinegar it will keep at least a month in the fridge.
1 cup fresh mint, finely chopped
3 Tbsp. boiling water
2 Tbsp. sugar
4 Tbsp. white wine vinegar (or white wine)
Place the mint in a pitcher and pour the boiling water over it. Let stand 20 minutes to infuse the water. Add the sugar and vinegar or wine and stir well. Serve.