Preheat the oven to 150°C, fan 130°C, Gas Mark 2. A 23cm square baking tin should be greased and lined. Melt the golden syrup, sugar, and butter in a small pot.
Combine the remaining ingredients in a large mixing basin, then pour in the warm butter and syrup combination. Stir to incorporate, then spoon into the tin, pressing down with the back of a spoon to flatten the mixture.
Preheat oven to 350°F and bake for 25-30 minutes, or until golden brown. Allow it cool for 2-3 minutes before cutting into squares. Remove from the oven once it has cooled.