This is an odd cake to make, but well worth the effort. Very rich, but different as it has no leavening except for that created by beating the batter.
You can substitute raisins for the currants, but currants do have a distinctive flavor which I prefer over raisins.
Cool in pan until completely room temperature. To serve, you can leave in pan or turn onto a platter. Cut into 18 small pieces as cake is very rich. No need to frost (although tradition suggests a light dusting of powdered sugar, sometimes in the shape of a cross if the cake is made in individual serving sizes).
The recipe card did not indicate a ratio of lemon peel to orange peel. I think I used a 3:3 ratio of lemons to oranges (as in, the peel of three lemons and the peel of three oranges, but because lemons are smaller than oranges, you get less peel, so I think it works out more like 2:3 lemon peel to orange peel by volume).
You can use dried, of course, but I have not tried it (if you do, remember to reduce by half or 2/3 the amount...so, I think that means you would use 3 tablespoons of dried peel instead of 2/3 cup of fresh...maybe) (fyi, math was not my strongest subject! Take my advice at your own risk!).