Preheat the oven to 170 ° C (top / bottom heat). A square 18-cup cake pan or a muffin pan for mini muffins - I recommend, but anything is possible - lightly grease or line with baking paper or paper liners.
For the shortbread dough, put the flour and sugar in a large bowl. With clean hands, knead the butter into the mixture until a batter is formed.
Press evenly on the bottom of the muffin or cake pan. Then bake in the oven for 15-20 minutes or until golden brown.
While the dough is baking in the oven, put the condensed milk, syrup, sugar and butter in a saucepan. Cook over low heat for about 5 minutes, stirring constantly.
This will take a while, but it must be done carefully, otherwise it will stick to the pan and burn. Watch carefully to see if it turns a deep caramel color, pour over the shortbread.
Let cool for 30 minutes or more, then pour the melted chocolate over the top. To do this, melt the chocolate in a microwave and stir the chocolate every 15 seconds.
Place in the fridge for another 30 minutes and then, when baked in the cake pan, cut into squares.
Tip:
The cake / muffins can be stored very well in the freezer for several weeks. It`s also handy to keep them in the freezer until just before serving.