Preheat oven to 425°F (220°C). Line a 12-cup muffin pan with paper liners.

Mix ½ cup all-purpose flour and ½ cup granulated sugar in a small bowl.

Work ¼ cup cold salted butter into the flour mixture until you have pea-sized crumbles. Refrigerate the streusel topping.

Whisk 2 cups all-purpose flour, 2 teaspoons baking powder, ½ teaspoon ground cinnamon, and ½ teaspoon salt in a medium bowl. Set aside.

Cream ⅓ cup butter and ¾ cup granulated sugar in a large mixing bowl with an electric mixer on high speed for 2 minutes.

Add 2 large eggs and 1 teaspoon vanilla extract, then mix on low speed until combined. Increase to high speed and beat for an additional minute.

Alternate adding the flour mixture and ½ cup milk with the mixer running on low speed until incorporated. Fold in 1 heaping cup of chopped peaches.

Divide the batter evenly among muffin cups, filling each almost to the top. Place remaining peaches on top and sprinkle with streusel mixture.

Bake at 425°F (220°C) for 5 minutes, then reduce temperature to 350°F (177°C) and bake for an additional 15-18 minutes, or until a toothpick inserted comes out clean.

Cool in muffin pans for 5 minutes, then transfer to a wire rack to cool for 10 minutes before serving.