Melt unsalted butter in a large skillet over medium-high; add minced sweet onion, and cook until softened, about 5 minutes. Stir in fresh corn kernels and water. Cover and cook 10 minutes. Transfer half of corn mixture to a blender. Remove center of blender lid; secure lid, and place a clean towel over opening. Process until smooth. Add puree to skillet; stir in heavy cream, kosher salt, pepper, and nutmeg. Cook over medium until thickened and heated through. Garnish with chopped fresh parsley.