To make the Streusel Topping combine the Brown Sugar (3 tablespoon), All-Purpose Flour (2 tablespoon), Unsalted Butter (6 tablespoon), Oatmeal (3 tablespoon), Pecans (2 tablespoon), Ground Cinnamon (1/4 teaspoon), Ground Ginger (1/4 teaspoon), Ground Nutmeg (1 pinch), and Salt (1 pinch) in a food processor and pulse until combined and crumbly. Set aside.
Set oven rack to the center and preheat oven to 350 degrees F (175 degrees C). Grease or line a 12 cup muffin tin.
Peel Peach (4) and remove the pit. Chop two of the peaches into 1/2-inch chunks and set aside. Puree the remaining two peaches using a blender or food processor until smooth. Set aside.
In a small bowl whisk together All-Purpose Flour (1 cup), Whole Wheat Flour (1 cup), Baking Powder (2 teaspoon), Baking Soda (1/2 teaspoon), Ground Cinnamon (1/2 teaspoon) and Kosher Salt (1/2 teaspoon). Set aside.
In a large bowl whisk together Canola Oil (1/3 cup) and Granulated Sugar (1/3 cup). Add Egg (2), one at a time, whisking after each until incorporated.
Stir in Sour Cream (1/3 cup), pureed peaches and Vanilla Extract (1 teaspoon). Whisk in dry ingredients until just combined (do not overmix). Fold in chopped peaches.
Divide batter evenly into prepared muffin tin. Sprinkle each muffin with a generous tablespoon of streusel topping.
Bake for 18-22 minutes, or a toothpick inserted in the center comes out clean.
Allow to cool at least 5-10 minutes prior to removing from muffin tin. Remove to a cooling rack to cool completely or eat while warm.