01 - Preheat oven to 400°F. Line a 12-cup muffin tin with paper liners or grease thoroughly with cooking spray.
02 - In a large mixing bowl, whisk together flour, baking powder, baking soda, and salt until evenly blended.
03 - In a separate bowl, whisk together oil or melted butter, sugar, eggs, milk, and vanilla extract until smooth and fully incorporated.
04 - Pour the wet ingredients into the dry ingredients. Gently fold with a spatula just until combined—stop as soon as flour disappears. The batter should remain slightly lumpy.
05 - Gently fold the diced strawberries into the batter until evenly distributed. Take care not to crush the fruit.
06 - Divide batter evenly among the prepared muffin cups, filling each about three-quarters full.
07 - Sprinkle the tops of each muffin generously with coarse sugar for a crunchy finish.
08 - Bake for 22 to 25 minutes, or until a toothpick inserted into the center comes out clean and the tops are golden brown.
09 - Let muffins cool in the pan for 5 minutes, then carefully transfer to a wire rack to cool completely.