Grease the tin with a little butter OR line the base with baking parchment or a linerThe advantage of lining the tin is that it's easier to clean and the finished cake comes out more easily
For the Polish Cake:
Crush the biscuits: Put the biscuits in a large bag. Beat with a rolling pin until the biscuits are in small piecesSome of the biscuit will be powdered and some will be in larger pieces - that is what you want
In a large saucepan, melt the butter, sugar, and golden syrup and mix well. Turn off the heat and add the crushed biscuits and cocoa. Mix thoroughly. The chocolate colour should be quite evenly distributed
Press the mixture into the tin with the back of a spoon. Push it down firmly. Turn the spoon over and use its edge to tidy up the edges of the cake base
Leave to cool.
For the topping:
When the base has cooled, tip it out of the tin and remove the liner
Melt the chocolate. Put the chocolate in a small basin and EITHER melt in the microwave on 30-sec bursts OR Put the basin over a saucepan of hot water. Don't let the water boil or touch the bowl. Keep stirring.For step-by-step instructions see How to Melt Chocolate
When the chocolate has melted, pour over the base and spread evenly using a knife
Leave to cool, then cut into squares
Notes
Everyday Cooks tips:
If the cocoa has lumps, don't bother to sift it. Just make sure you mix it in thoroughly, pressing the lumps out as you go
Storage:Polish Cake keeps well for a week or so in an airtight tin or plastic box. It will keep for longer in the fridge, but the chocolate may look less shiny.