In a small bowl, mix flour, brown sugar, and cinnamon together for the streusel. Add cold butter and rub it in using your fingertips or a fork until the mixture turns crumbly. Set it aside while you prepare the batter so it stays firm and bakes into a crunchy topping.

In a large bowl, whisk together all dry ingredients so everything is evenly combined. This ensures the muffins rise properly and the flavor is balanced in every bite.

In another bowl, whisk eggs, buttermilk, melted butter, and vanilla extract until smooth and well combined. This wet mixture is what makes the muffins soft, moist, and rich in flavor.

Pour the wet ingredients into the dry ingredients and gently mix until just combined. Be careful not to overmix, as this can make the muffins dense instead of light and fluffy.

Gently fold in the chopped peaches so they are evenly distributed throughout the batter. Try to keep the pieces intact so you get juicy bites in every muffin.

Spoon the batter into the muffin tray, filling each cup about ¾ full. Sprinkle the prepared streusel generously on top of each muffin to create a sweet, crunchy topping after baking.

Bake for 18–22 minutes, or until the tops are golden brown and a toothpick inserted in the center comes out clean or with a few moist crumbs.

Let the muffins rest in the pan for about 5 minutes, then transfer them to a wire rack to cool slightly. They taste best warm when the peaches are juicy and the texture is soft and tender.