This isn't my recipe so if it doesn't work don't blame me, it's my favourite, Anna

Macaroon Bars:

Ingredients:

One small potato (seriously, no kidding)
Lots of icing sugar (you can need as much as two pounds in weight, depending on
the size of your potato).
Dessicated coconut.
Cooking chocolate (better to have too much to hand than too little).

Peel and boil the potato (without adding salt!!!!!!!).
Mash the potato with a fork.
Begin adding icing sugar.
The mixture will become very moist as you do so.
Keep adding icing sugar gradually till the mixture thickens (I can't tell you
precisely how long; it comes with practice).
When the mixture is stiff enough to be moulded into a long bar shape, without
sticking to the worktop, it is time to stop adding icing sugar.
Cover the work surface with icing sugar, and work the mixture into a long thin
bar that retains its shape easily.
Cut the length into lengths of three or four inches (there is no right or wrong;
it's all personal preference).
Toast lots of dessicated coconut under a grill (you can be haphazard about this;
some of the coconut will be darker than other bits; this gives you the
characteristic macaroon bar appearance).
Put the toasted coconut into a large bowl or deep tray.
Melt the cooking chocolate. (I prefer using the microwave to do so; the aim is to
melt it without getting it too hot).
One at a time, dip the short lengths of macaroon mixture (i.e. the potato and the
icing sugar) into the melted chocolate. Turn over to make sure it's covered top,
bottom and sides (this is messy but fun).
Place the chocolate-covered mixture into the coconut, and cover generously.
Place the bar on a plate and allow the chocolate to dry.
The results are excellent, and the bars keep fresh for two to three weeks