Preheat oven to 350°F. Line standard 12-cavity muffin tin with paper liners. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or using an electric hand mixer), cream together butter and sugar until smooth. Scrape down sides of bowl as needed for thorough mixing.
Add sour cream, egg, mik and vanilla. Mix until well combined.
In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Add dry mixture to mixing bowl. Mix on low speed until batter is smooth, thick, and well combined. Scrape down sides of bowl as needed to ensure thorough mixing.
Fold in fresh peach chunks until evenly distributed. Use a size 24 scoop (3 ½ Tablespoons) to distribute batter among prepared muffin tin. Sprinkle ½ Tablespoon streusel. Follow with a size 40 scoop (1 ½ Tablespoon) of batter on top on streusel. Finish by adding 1 Tablespoon of struesel to cover batter.
Bake for 25-28 minutes until a toothpick inserted in center of muffin comes out clean. Allow muffins to cool in pan for 5-7 minutes before unmolding. Allow muffins to cool on wire rack. Serve muffins warm or at room temperature.