Preparation Bring water, oil, and sea salt to a boil in a 4-quart heavy pot, then add polenta in a slow stream, whisking. Cook over moderate heat, whisking, 2 minutes. Reduce heat to low and cook at a bare simmer, uncovered, stirring frequently with a long-handled spoon, 45 minutes. Remove from heat, then add butter and stir until incorporated.
Preparation Bring water, oil, and sea salt to a boil in a 4-quart heavy pot, then add polenta in a slow stream, whisking. Cook over moderate heat, whisking, 2 minutes. Reduce heat to low and cook at a bare simmer, uncovered, stirring frequently with a long-handled spoon, 45 minutes. Remove from heat, then add butter and stir until incorporated.