Preheat the oven to 200C/180C Fan/Gas 6. Line an 8" square baking tin.
Make the shortbread by combining the butter, sugar and flour on high in a food processor/with an electric mixer. The mixture should be crumbly but hold together when 'squeezed'. Press into the square tin, levelling out. Bake for 20-25 minutes, until golden brown.
While the shortbread is in the oven, make the brownie layer:
In a small bowl, break up the dark chocolate and melt in the microwave in 20 second intervals, stirring in between to make sure it doesn’t burn.
In a large mixing bowl, whisk together butter and both sugars for 3-5 minutes. Add in the eggs, one at a time and mixing in between. Add the vanilla and mix again.
Now, add the chocolate slowly (check it first, to make sure it isn’t so hot that it will cook the eggs) and combine once again.
Gently fold in the flour and cocoa powder.
Once the shortbread has finished baking, and has cooled for at least 5 minutes, spread over the caramel.
Pour over the brownie batter and bake for 30-35 minutes. Remove, cool on a wire rack and slice. (Cool in the fridge once it reaches room temp for really neat squares).
