Key lime pie 2

A return to a favourite theme of this blog: the creamy pie with a biscuit base. (See here, here, and here.) This one is adapted from a recipe in Nigella Lawson's KITCHEN. Hers has twice as many (ordinary) digestives, with 50g chocolate chips. You'd be able to use a better class of chocolate that way than you'd get from my chocolate digestives.

Nigella uses only 50g of butter to 300g of biscuits, while I have always believed that a higher ratio of butter gives you a firmer base. And she whizzes up the butter with the biscuits and chocolate: I had never thought of doing that, always stirring the crumbs into butter melted in a pan. The drawback of her method is that the mixture resolves itself into a ball in the food processor, rather as flour and fat do when you add a little water. It is a bit of an effort to spread it out in the dish.

150g chocolate digestives (I used gluten-free)
1tsp cocoa powder
75g unsalted butter, cut into pieces
1 397g can condensed milk
3 limes, juiced and zested
284ml double cream

Whizz the biscuits with the cocoa powder and butter in a food processor.

Grease a 20cm flan dish or a springform tin. Tip in the biscuit mixture, spread it out, compact it with the back of a spoon, and put the dish or tin into the freezer for 30 minutes, to firm up the crumbs.

Pour the condensed milk into a bowl. Stir in the lime juice and zest, and pour in the cream. Whisk. With a hand whisk, this is quite hard work. The mixture does not go stiff, but it does, eventually, thicken. Pour this filling on top of the biscuit base.

Cover the dish with foil, tented at the top so that it does not stick to the filling, and refrigerate for at least three hours, or overnight.

This pie has an ideal combination of crunchy base and creamy, but light and tangy, filling.