Preheat oven to 350 degrees.
In a medium-sized mixing bowl, whisk together your fresh milled flour, baking powder, baking soda, salt, cinnamon, and any extra spices of your choosing. Set aside.
In a separate bowl (large mixing bowl or stand mixer), cream melted butter, sugar, sourdough starter, vanilla, and eggs.
Slowly add your dry ingredients to your wet ingredients and mix until combined. Toss in any extras (fresh blueberries, mini chocolate chips, etc) and lightly fold into your batter.
Grease the muffin tin with a stick of butter, melted coconut oil, or oil of choice, or line the muffin pan with muffin liners.
Scoop the muffin batter into the pan.
Place muffins into your preheated oven to bake for 12 min.
Let them cool before enjoying.