Preheat the oven to 325°F (about 160℃).
Grease an 8 x 8 inch square pan lightly.
Mix everything together thoroughly in a large bowl using a wooden spoon. (It really is that easy!)
Transfer the mixture into the baking pan, pressing it down lightly.
Bake for 20 to 25 minutes or until very pale golden brown. I always check after 15 minutes and regularly thereafter.
Cool on a wire rack.
When the squares are completely cool, make the icing.
Blend together butter and icing sugar in an electric mixer.
Gradually add enough milk, cream or half and half to make a spreadable frosting.
Spread the frosting over the cooled squares.
Melt the chocolate carefully drizzle over the icing.
Cover and place the pan of squares in the fridge to chill. Cut in small squares when cold.