Preheat oven to 375 degrees F (190 degrees C). Grease muffin cups or line with paper liners.
In a large bowl, stir together the flour, baking powder, baking soda and salt. In a separate bowl, cream together the butter and sugar. Beat in the eggs, one at a time, then stir in the vanilla. Add the butter mixture to the flour mixture, stirring just until moistened. Fold in the strawberries and blueberries.
Fill the muffin cups about three-quarters full. Bake for 20 to 25 minutes in the preheated oven, until a toothpick inserted into the center of the muffin comes out clean.
Let cool in the pans for 10 minutes before transferring to wire racks to cool completely.
Interesting Facts
Strawberries are packed with Vitamin C, which helps to boost the immune system.
Blueberries are a good source of fiber, which helps to keep you feeling full for longer.
Muffins are a great way to use up any extra fruit you have lying around in the fridge.