Actually, I bought a citrus zester in a posh cook shop in Broadway years ago, which is now getting a little blunt. But a good cheese grater will do just as well. Yes, and then chop it but not to finely.
The secret is not to add any water....there will be plenty of fluid with the berries and orange juice. Its also not something that you can walk away from, as it will stick to the pan if left ! ( I forgot to say that I add sugar to taste...a little at a time, as you can't take it back out once its in )
This sauce should be a tad on the tart side, although I suppose I make it sweeter now than I used to. I add the Port towards the end. If you have had some of the sauce in the fridge for a while, it does get quite thick, so a good slug of Port will help it no end !
I used to make a version with gooseberries and a dry Sherry.
This goes quite well with any fatty meat, or cheese or, to be honest, pretty much anything else ! ( its wonderful for hiding the taste of the Devils Food...the ruddy sprouts ! )