Preheat oven to 350 degrees F. Line a 12 cup muffin pan with paper liners or spray with baking spray.

Batter:
In a medium bowl, whisk together 1-1/2 cups flour, baking powder, salt and baking soda. In a small bowl, whisk together 1/3 cup milk, sour cream and 1-1/2 tsp vanilla.

In the bowl of a stand mixer, beat granulated sugar, and butter on medium high speed until light and fluffy, 3-4 minutes. Add egg beating until combined, stopping to scrape down sides of the bowl. With the mixer on low speed, add flour mixture alternatively with the milk mixture, beginning and ending with the flour. Beat well between each addition and stop as needed to scrape down bowl. 

In a medium bowl add the 3/4 cup peaches and 1 Tbsp flour. Toss to coat the peaches. Add peaches to muffin batter and gently fold until just combines.

Divide batter between muffin cups. Top with 1/4 cup[ peaches and streusel topping.

Bake until a wooden pick inserted into the centers comes out clean, about 20 to 25 minutes. Let cool in pan for at least 10 minutes, then transfer to rack to cool.