The Fluffiest White Bread in the World

Name: The Fluffiest White Bread in the World
Cuisine: World Cuisine
Ingredients: 1 large egg; 2⁄3 cup (160 g.) whole milk at room temperature (about 75°), plus more for brushing; 3 tbsp. (40 g.) slightly warmed water (about 85°F); 2 1⁄3 cups plus 1 Tbsp. (340 g.) bread flour; 1⁄4 cup plus 1 tsp. (60 g.) sugar; 1 1⁄4 tsp. (4 g.) instant dry yeast; 2 tsp. (6 g.) kosher salt; 1⁄4 cup (60 g.) unsalted butter, at room temperature; Nonstick baking spray, or a neutral-flavored oil, for greasing