Preheat oven to 180°C/356°F
Beat butter, sugar and yolk in a small bowl with electric mixer until smooth. Stir in remaining sifted dry ingredients.
Press mixture evenly over base of greased 19cmx29cm rectangular slice pan.
Bake for 20mins or until lightly browned.
Stand base for 5mins then spread with hot topping and bake for a further 5mins at 180c. Cool in Pan.
Combine sugar, golden syrup and butter in medium pan, stir over heat until butter is melted. Bring to boil, simmer stirring for 3mins or until mixture darkens and thickens slightly. Stir in nuts.