Preheat the oven to 375 degrees F. Line 12 large muffin cups with paper liners, and spray the top of the pan lightly with nonstick spray.
In a medium bowl, sift together the dry ingredients, from flour to salt, and set aside.
In a separate bowl, whisk the eggs, butter, sour cream, and vanilla. Fold in the peaches.
Add the egg mixture to the dry mixture. Stir until just moist and blended. Do not overmix.
Scoop the batter into the prepared muffin pan with a large ice cream scoop (1/3-cup scoop).
Sprinkle with the Brown Sugar-Walnut Streusel Topping, and lightly press the topping into the muffin batter
Bake 30 to 35 minutes, until the tops of the muffins spring back when lightly pressed and a toothpick inserted in the center of a muffin comes clean. Remove from the oven, and cool for 5 minutes. Turn the muffins out of the pan, and serve immediately.