Long ago, probably about the time I left home and went to college, I started a recipe book, and one of the first recipes I copied into it is this one for lemon syrup - in other words, home made lemon squash - and I've been making it ever since. I have no idea where the recipe came from though.
Just before I made it last time, I was in Ikea and saw this lovely old style lemonade bottle, and I thought it would be perfect for the syrup. Of course, it was too good to be true - the bottle is too tall to fit into our stupid fridge door - but the syrup turned out fine and it still looks very pretty so I can't really complain!
2 lemons, preferably unwaxed
1¾ lb/800g granulated sugar
1pt/600ml boiling water
1oz/30g tartaric acid
Peel the lemons thinly with a vegetable peeler (a zester is a waste of time here) and add to the sugar. Pour on the boiling water and stir occasionally until the sugar has dissolved. In the meantime, juice the lemons and mix the juice with the tartaric acid. Mix this into the peel and syrup, and once everything is dissolved, bottle and store in the pantry or fridge.
You'll need about 2 tbsp per glass of water.
Tartaric acid is an antioxidant (and acts as a preservative) so the syrup keeps for months. You could probably even keep it on the kitchen counter if you live somewhere coolish (but probably not the Bahamas).
If you want to do as I did, and keep it in a fancy bottle, I suggest you make it directly in the bottle, ie. put the sugar in the bottle and pour the boiling water directly in (don't forget to leave a bit of room to add the lemon juice). In my case, there wasn't room in the bottle for the whole pint of water so I ended up with a more concentrated syrup, but that's hardly a problem.
I'd also like to try this with grapefruit. I think one lemon and one or two grapefruits should do it, but not the pink ones - I think this would need some proper grapefruit acidity to really taste good.
ps. don't worry! you will get the lemon peel out of the bottle!