||First, place the water in a pot. Add 25g butter and bring to the boil. Once the water is bubbling, slowly empty the polenta into the pan, stirring all the while with a whisk.
||Meanwhile, very lightly grease a baking tray, approximately 34cm by 25cm wide and a couple of centimetres deep.
||Reduce to a low-medium heat and continue stirring through – here you may want to switch to a wooden spoon. Keep stirring for 5 minutes or so until it begins to thicken.
||Add the butter and stir through, which will loosen the polenta up a bit. Add the Gruyère cheese, again still stirring so that the cheese melts and incorporates into the polenta. Taste for seasoning, grinding in a good mix of salt and pepper
||Working quickly, pour the polenta into the tray, giving it a good shake to distribute the ‘porridge’ evenly into the corners.
||Cover with a tea towel and leave in a cool part of the kitchen to set fully – this takes about 1–2 hours.
||Turn out the slab of polenta onto a chopping board. Cut into thin slices and set aside.
||Heat oil in a pan and sea