Cooking oil spray, to grease
350g unsalted butter, chopped, softened
1 cup caster sugar
1 3/4 cups plain flour
395g can sweetened condensed milk
1/4 cup honey
1/3 cup chopped walnuts
200g dark chocolate, melted
Preheat oven to 180C. Grease a 26 x 16cm slice tin and line base and sides with baking paper. Put 225g of the butter and 1/2 cup of the sugar in the large bowl of an electric mixer and beat until light and fluffy. Add flour and stir to combine. Press mixture evenly into prepared tin and smooth surface. Bake for 25 minutes or until golden.
Put remaining butter and remaining sugar in a medium heavy-based saucepan over low heat. Stir until butter is melted. Add condensed milk and honey and cook, stirring constantly, for 10 minutes or until a thick caramel forms. Remove from heat, add walnuts. Stir to combine. Pour caramel over base. Cool to room temperature.
Pour over melted chocolate and spread to coat. Chill for 3 hours. Cut into squares. Serve chilled.