Melt the butter, sugar and golden syrup in a saucepan on a low to medium heat.
Mix the dry ingredients in a large mixing bowl.
Pour the melted mixture onto the dry ingredients and stir until well incorporated.
Pour the batter into your tin. Spread to the edges and pack the mix flat with the back of a wooden spoon to compress it a little. This prevents crumbling.
Bake for 25-30 minutes in the middle of the oven.
Allow to cool completely in the tin before cutting into rectangles.