Preheat oven to 200°C.
Line a 12 cup muffin tray with muffin cases; set aside.
In a large bowl, combine flour, oats, brown sugar, baking powder and salt.
In another bowl, whisk together butter, sour cream and egg. Pour mixture over dry ingredients and stir until moist.
Add peaches and gently toss to combine.
Scoop the mixture evenly into the muffin tray.
Make your topping by measuring out flour, brown sugar, cinnamon and cardamon into a small bowl.
Mix 2 tablespoons of butter into your mixture until it looks like crumbs. Sprinkle over each muffin.
Place into oven and bake for 16-18 minutes, or until a tester inserted in to the centre comes out clean.
Remove from oven and cool on a wire rack.