Put the butter, measurement water and salt in a heavy-based saucepan and bring to the boil. Put the polenta in a jug and pour into the water mixture in a slow but steady stream, stirring vigorously with a wooden spoon to prevent lumps forming. Reduce the heat to a slow simmer and cook, stirring frequently, for about 5 minutes, or until the polenta is thick and comes away from the side of the pan.
Transfer the polenta to a shallow oiled dish, smooth the top and leave to cool. Cover and chill until firm.
Turn the polenta out on to wet greaseproof paper and cut into thick chips with a wet knife.
Heat enough oil for deep-frying in a deep saucepan to 180–190°C (350–375°F), or until a cube of bread browns in 30 seconds. Roll the chips in a little flour to coat, add to the hot oil, in batches, and cook for 6–8 minutes until pale golden brown and crisp. Remove with a slotted spoon and drain on kitchen paper. Sprinkle with salt and paprika. Keep warm in a low oven with the door ajar until ready to serve.