I tried giving my mice a blob of creamed coconut on my finger, and they practically chewed my finger off! :P
They absolutely loved it!
It'll be a rare treat, as it's very high in fat, but I think it'd be particularly suitable for poorly or underweight mice (rats too I expect), as it's got lots of energy and vitamins in it. :) Could also be useful for training or giving medication to mice not so keen on malt paste.
You can buy it from the supermarket (try the exotic foods aisle), or I got it from Rat Rations
for about 80p. :)