Peach Muffins with Unsalted Butter

Instructions:

1. Toss the diced peaches in 1 tablespoon of flour to prevent them from sinking during baking.
2. Preheat the oven to 425°F (218°C).
3. Whisk the melted unsalted butter and granulated sugar together until smooth.
4. Stir in the egg and vanilla extract until the mixture is pale and glossy.
5. Fold in the all-purpose flour, baking powder, and salt, alternating with the milk; stir only until no streaks of flour remain.
6. Gently fold in the floured peaches using a spatula.
7. In a small bowl, cut the chilled butter into the brown sugar, flour, and cinnamon until the mixture resembles coarse wet sand.
8. Fill muffin cups to the brim and generously heap the crumble topping on each muffin.
9. Bake at 425°F (218°C) for 5 minutes, then reduce the oven temperature to 350°F (175°C) and bake for the remaining 15 minutes until the tops are mahogany-colored and a toothpick comes out clean.