Not sure if this helps but I make Nigella's Clementine Cake. Her recipe states to simmer clementines much like your mandarins. I found a useful time saving tip to cook the fruit whole in the microwave. I put my fruit in a microwave able bowl, add water (about a third of the way up the fruit) put a lid on the bowl and cook on high for 10 minutes (I do start checking after 5 minutes and turn my fruit over). When the fruit is cooled - I then blitz the contents of the bowl; water, peel etc to a purée. I also buy the larger bags of clementines, because I pour my puréed fruit into freezing bowls and freeze. When frozen transfer purée from bowl into freezer bags (gives me use of bowl back). When I want to make a cake - I remove purée from freezer bag and defrost the purée in the original freezer bowl overnight. The next morning the mixture may have separated a little but this is fine - stir and use all the liquid, don't be tempted to throw the watery looking liquid away.
Increase microwave cooking time as required for double or more fruit quantities.
Hope this helps
Shally
