Boil water in a saucepan. Add grits and 1/4 teaspoon kosher salt, stirring constantly. Bring to a boil; cover and reduce heat to low. Cook 7 minutes or until thick, stirring frequently. Melt butter in a nonstick skillet over medium heat. Add mushrooms, minced garlic, pepper, and 1/8 teaspoon kosher salt; cook 8 minutes, stirring occasionally. Stir mushroom mixture into grits. Top with parsley.