Heat oven to 190C/170C fan/gas 5. In a large saucepan, bring the stock to the boil. Slowly pour in the polenta, a little at a time, until completely absorbed. Lower the heat, stir quickly for 5 mins, then remove from the heat altogether. Stir in 1 tbsp of the Parmesan, then spread the polenta out on a large parchment-lined baking sheet, so that it’s 2-3cm thick.