Granny's birthday cake ('Petit Beurre koek')

This cake features in some of my fondest memories and is my favourite guilty pleasure, second only to dark Belgian chocolate. It is terribly rich and a small serving is loaded with enough sugar and caffeine to keep your children up all night and possibly the next too. But they love it, as do my colleague scientists (no comment on the similarity there!). 

Moreover, you don't need to be a kitchen princess/prince to pull it off. Take it from someone who can't even boil an egg properly :-) All you need is 4-5 cheap ingredients, some manual mixing and an interest in assembling or brick laying. You can try out different mixes of ingredients to get different tastes, or be inaccurate in your measuring, and your cake will still get compliments. Also no oven required so kids can easily make their own from start to delicious finish.

This recipe is quite well known in Belgium and everyone had their own variation and tricks. I'll share mine, which means mainly granny's but also the adaptations I've made to accommodate the fact that some ingredients are hard to come by in the UK. 

Ingredients for feeding 6-8 persons (or possibly 4-6 little persons/scientists):

- instant coffee (25-50 g depending on your caffeine tolerance)
- icing sugar (100-250 g depending on how big your sweet tooth is)
- 250 g of soft butter
- cookies: Petit Beurre (Belgium), Leibniz without chocolate (Germany), malted milk biscuits (UK) or your local equivalent (you'll want a fairly soft buttery rectangular cookie)
- optional chocolate sprinkles/hundreds-and-thousands or cocoa powder

Begin by taking the butter out of the fridge so it can soften, making it easier to mix with. Boil some water in a large mug / bowl and stir in the instant coffee. Granny recommends to use as much coffee as you can dissolve in the water without clumps appearing. I'd say around 25-50 g depending on how strongly you'd like it to taste of coffee. It should definitely (/hopefully) be a lot more than your regular portion when making coffee to drink! Stir well then leave to cool down. 

When the butter is soft & coffee cold, add the icing sugar. Granny says to use as much sugar as you have butter, but I tend to use a little less than that (about 150-200 g). It's a matter of taste; experiment to find your own (great excuse for sampling the mix till it's perfect!). Mix the butter and sugar (I do it by hand). Next, mix in a few coffee spoons of coffee (about 2-6 spoons, again, try out different tastes). The mixture should be very easy to mix by now. 

The original recipe asks for chocolate sprinkles to be, ahem, sprinkled over the cake at the end. However, if you don't have/like those but still want a chocolaty taste, try adding a few coffee spoons of cocoa to the mixture now. This really depends on your cocoa, so add in one spoon at a time, mix, and taste before deciding whether to add another one. Isn't experimenting awesome? :-)

Whether or not you've added cocoa, your mixture is now ready to use. Have the bowl of cold coffee, the cookies, a tray/plate and a knife nearby and pull up a chair. Time to start the brick laying!

For the bottom layer of cookies, dip only the top half of the cookie into the coffee, then arrange on the plate. This will ensure a firm baselayer. Next, evenly spread some of the butter mixture over this layer. This will be the cement that hold the different layers of cookies together.

For the next layers of cookies, dip them fully in the coffee but don't leave them in too long to prevent them from becoming too soggy. Can't easily spread the butter mixture on top of the cookies if they disintegrate at the slightest touch! Continue interleaving layers of coffee soaked cookies with layers of the butter mix. Finally, finish off the brickwork by adding a layer of butter mix on top as well as on the sides, hiding the cookies from view and providing a sticky layer to optionally sprinkle those hundreds-and-thousands across.

Put the cake in the fridge and let it all settle (e.g. overnight). Keep the cake in the fridge (should be ok for a few days) and take it out about 15 minutes or so before serving it (so it can soften a bit again) for the best result.

This cake lends itself quite well to experimenting and decorating, and it's really easy to fall in love with its simplicity, and its sugary caffeinated taste...