Sly Cakes were traditional in Lancashire, England.
A Sly Cake consists of two layers of sweet, unleavened pastry, with a filling in between of a spiced mixture of dried fruit.
You seal the edges of the two layers, and bake it.
The pastry is made in a way remiscent of puff pastry, with a few foldings with a fat between each layer.
The base for the fruit mixture is currants; they may be mixed with raisins, dried figs, walnuts, etc.
Some recipes have you soak the dried fruit in rum; others have you simmer it in water instead.
Lancashire Sly Cakes
12 ounces flour (2 1/4 cups / 350g)
12 tablespoons of soft butter
3 tablespoons castor sugar
1/2 cup currants
A pinch of salt
A pinch of mixed spice
(optional: dried figs, raisins, walnuts)
(optional: brown sugar to sweeten the fruit mixture)
Some time before starting, steep the currants in rum which should just cover them, along with any of the optional dried fruit or nuts.
Mix together the flour, sugar, salt and spice then form into a stiff dough with cold water.
Roll the dough into an oblong. Spread 4 tablespoons of the butter on top. Fold one side into the centre, then fold the other side into the centre. Seal the edges and half-turn so that the sides are now top and bottom. Roll it back out into an oblong, and repeat the above step 2 more times, each time using 4 tablespoons of the butter.
Drain the fruit; stir in a bit of brown sugar if desired.
Roll the pastry dough out thinly. Cut into rounds. In the centre of each round put a bit of the fruit mixture. Top with a round of pastry, and seal the edges.
Prick each with a fork a few times; put onto a greased baking sheet; bake at 350 F / 150 C for 25 to 35 minutes, until golden brown.
Some people guess that Sly Cake is perhaps called “Sly” because it looks like nothing is in it.