Chocolate Biscuit Cake

This is known in my family as Evil Biscuit Cake. Rather heavy on calories! It's not really a pudding.

Ingredients
digestive biscuits
butter
dark chocolate
white chocolate
a tin of sweetened condensed milk ( )

Equipment
saucepan
2 bowls
spoon square baking tin
baking paper (optional)
knife

preparation time:
break up biscuits
melt chocolate and butter
mixing ingredients
several hours setting in fridge

Cooking process

Break up the digestive biscuits in a big bowl. The pieces should be faitly small, but you don't want them pulverised. I find this easiest by hand (usually watching TV!)
Put some water in the saucepan and put another bowl in the water. Don't put too much water in; it should reach about half way up. Break up the dark chocolate, and roughly cut up the butter, and put it in the bowl. Heat the saucepan until the butter and chocolate just melts. (Making the chocolate and butter into small pieces speeds this process). Take it off the heat immediately everything is melted. Add the condensed milk and stir.
Pour and scrape the chocolate mix on top of the biscuit bits. Mix. Chop the white chocolate into small pieces. Mix them in as well.
Line the baking tin with baking parchment. This is optional, but will help you lift out the biscuit cake when cooked. (You can do this while the chocolate is melting).
Turn the mix into the tin. Do this a spoon at a time; this mix isn't very eay to push around. Try to get it into the corners and smoothish on top.
Put in fridge until hard. This will be several hours; I tend to leave it overnight.
Lift out the biscuit cake and peel off the paper. Cut the biscuit cake into small pieces. These are usually cut into quite large pieces, but I prefer small pieces, and let people eat several at a time if they want.
If you are storing it, put it in layers with some greaseproof paper between each layer, or it will stick together. I use the baking paper that lined the tin. It's probably best to store it in the fridge as it gets stickky quite easily otherwise.

Other ideas

You really must use dark chocolate for this. Milk chocolate doesn't melt as well, and anyway, dark chocolate is often of a better quality. I use Fair Trade chocolate. The white chocolate is really optional, but those nuggets of hard white chocolate make a lovely contrast to the biscuit. The amounts of chooclate can vary. I have used the same amount of white and dark chocolate, but the total amount should be about the same.
Sweetened condensed milk is a very specific ingedient. If you can't find it, don't use this recipe. It is thick and very sweet. Other types of tinned milk or any form of cream won't work.