Preheat the oven to 180°C conventional (160°C fan-forced). Line a 28 cm x 18 cm baking tray with baking paper.
For the base: Combine all the ingredients and mix well. Press into the tray and spread out evenly with a wooden spoon (it doesn’t have to be perfect). Bake for 25 minutes or until golden brown. Remove and let cool.
1 cup brown sugar, 2/3 cup fine yellow polenta, 3/4 cup self-raising flour, 1/2 teaspoon baking powder, 150 g butter
For the topping: Mix the melted butter, golden syrup and condensed milk in a heavy-based saucepan over medium heat. Stir constantly for about 15–20 minutes until the mix has thickened.
60 g butter, 1/4 cup golden syrup, 790 g sweetened condensed milk
Pour the topping over the base and spread out evenly. Sprinkle with sea salt and bake for a further 20 minutes or until golden in colour. Leave to cool in the tin before slicing.