Heat oven to 400° F. Brown the butter: Melt the butter in a skillet or small saucepan over medium heat. Swirl or stir the butter with a wooden spoon as it starts to foam and sputter. Remove the butter from the heat as soon as it begins to turn golden brown and smells nutty, about 1 minute. Remove from heat and let cool to room temperature. In a large bowl, whisk together the flour, baking powder, sugar, and salt. Gently stir in the brown butter and milk. On a floured surface, shape the dough with your hands into a 1/2-inch-thick disk. Cut the dough into 2-inch round biscuits. Place on an ungreased baking sheet and bake until the tops are lightly golden, 12 to 15 minutes. Serve warm with jam and clotted cream or butter. Tip: Brown butter adds richness to muffins, shortbread, and scones. Use it at room temperature as a substitute for the cold butter called for in your recipe.