1.Preheat oven to 160°C. Grease a 20cm x 30cm rectangular pan and line base and long sides with baking paper, extending paper 5cm over sides.
2.Beat 125g of the butter, caster sugar and egg yolk in a small bowl with an electric mixer until light and fluffy. Stir in sifted flours. Press mixture evenly over base of pan. Bake 15 minutes.
3.In a medium saucepan over low heat, stir honey, brown sugar and remaining butter until sugar is dissolved. Bring to the boil. Boil, uncovered, without stirring, 2 minutes. Add cream and boil, stirring, for 1 minute. Remove from heat. Stir in nuts until coated in caramel mixture. Working quickly, pour nut mixture over base and spread evenly with spatula.
4.Bake a further 15 minutes. Cool slice in pan. Refrigerate 2 hours before cutting.