1. Cream the butter and the sugar together.
Take butter out of fridge and cut into large slices and nuke in microwave until soft, gradually add sugar a bit at a time stirring with a large wooden spoon.
2. Add the flour to creamed butter and sigar.
Again seive the flour and add gradually to the butter/sugar cream. Use an electric whisk for laziness.
3. Form into a ball and leave for 30minutes-1hour.
This will allow the mixture to firm. Just leave it on the side with a tea towel over the top but dont return to fridge or the butter will go hard.
4. Roll into a flat piece around 3/4 inch to 1 inch thick and place on a raised side baking tray which you have already rubbed a bit of butter (using a piece of kitchen roll to do this is fine).
5. Bake for around 30 minutes in the middle of the oven at 180c.
6. Take out and leave to cool.
7. Fill a large saucepan with boiling water from the kettle and place on a medium heat hob. Place the tin of condensed milk into the water and simmer for 2.5 hours minimum (turning the condensed milk into toffee). Make sure you keep the water topped up and that it does not boil dry.
8. Leave condensed to cool then when can is cool to the touch open and spread the sticky toffee goodness over the shortbread you made earlier.
9. Leave in the fridge at least over night.
10. Melt 300grammes of Milk cooking chocolate in a bowl over simmering hot water.
11. When clocolate has melted take off the water and allow to cool for a few minutes.
12. Pour melted chocolate over the toffee topped shortbread and return to the fridge for several hours until chocolate is hard.
13. Cut into squares and serve (preferably with a nice coffee). Make sure the squares are around 2-3 inches square tops as it is sweet and a little sickly in excess.