Preheat your oven to 350°F, line a muffin pan with paper muffin cups and set aside.

Mix your dry ingredients (all-purpose flour, baking soda, baking powder, and salt) in a mixing bowl and set aside.

In a standing mixer, using a paddle attachment, beat together butter and granulated sugar for about 5 minutes until pale and fluffy.

When ready, add eggs, vanilla extract, and buttermilk. Mix well until all the ingredients are well incorporated.

Add dry ingredients, and using a spatula, fold it in.

Add peeled and diced peaches to the mixture and fold it in as well.

Divide the batter between 12 muffin cups.

In a smaller mixing bowl, mix together brown flour, sugar, cinnamon, and melted butter. Using a fork, mix together until you have crumbles.

Spoon the crumbles on top of the muffins and bake at 350°F for about 20 minutes or until a toothpick inserted in the middle comes out clean.

When the muffins are done, take them out of the oven and let them sit in the muffin tin for about 10 minutes, then remove them to a wire rack to cool off completely.

For the glaze, whisk together powdered sugar, milk, and vanilla extract and drizzle it over the muffins.