Preheat your oven to 400 degrees. Add the muffin liners to your muffin tin and set aside.
Add flour, baking powder, baking soda, salt to a bowl and whisk together.
In another bowl or your stand mixer, add granulated sugar, brown sugar, vanilla extract, avocado or coconut oil (melted), sourdough starter, milk, and the egg and whisk together until fully incorporated.
Gradually add the dry ingredients to the wet ingredients until the batter comes together.
Next, add the blueberries, raspberries, and white chocolate chips to the bowl.
Take a silicon spatula and gently fold the berries and chocolate into the batter.
Take an ice cream scoop or cookie scoop and add the sourdough muffin batter to the lined muffin tin.
Bake the patriotic sourdough muffins at 400 degrees for 25-30 minutes.
Stick a knife in the center of the patriotic sourdough muffins to check if they are baked through. If the knife comes out clean, they are done.
Allow the patriotic sourdough muffins to cool for 5 - 10 minutes.
For the icing, add powdered sugar and water to a bowl and whisk together. It's as easy as that!
Pour the icing into a ziploc bag and cut a tiny hole at the bottom. This will be your homemade piping bag for the icing.
Drizzle the icing on top of the patriotic sourdough muffins and add some festive sprinkles on top.