Preheat your oven to 375°F (190°C).
Grease your muffin tin or line it with paper liners.
In a large mixing bowl, whisk together the all-purpose flour, sugar, baking powder, and salt.
In another bowl, combine the milk, melted butter, and beaten egg. Stir until well combined.
Gently pour the wet mixture into the dry ingredients and combine without overmixing.
Add the blueberries to the batter, folding them in gently.
Spoon the batter into the prepared muffin tin, filling each cup about two-thirds full.
Sprinkle a little coarse sugar on top of each muffin.
Bake for 18-20 minutes or until a toothpick comes out clean.
Let cool for a few minutes before transferring to a cooling rack.
