Bring water to the boil. Add oil, garlic and salt. Rain in the polenta flour in a thin stream through your fingers, stirring constantly (Italian-style-always in the same direction) with a sturdy whisk or wooden spoon, for one minute.
Add butter and cheese. Stir through. (At this point I often add some extra flavourings e.g. finely chopped fresh herbs like rosemary, Italian parsley or thyme. Or some diced sundried tomatoes, diced grilled capsicums or diced, dried porcini mushrooms which have been steeped in hot water for 10 minutes. There are endless possibilities). Cover saucepan, turn off heat, and leave for 40 minutes. Remove lid, taste and adjust seasoning if required. Serve immediately.