In a medium bowl, whisk together the flour, sugar, baking powder and salt. In a small bowl, whisk together the egg, milk and vanilla. Preheat a nonstick griddle over medium heat.
Whisk the wet ingredients into the dry. Stir in the melted butter. The batter should be thick and smooth. Fold in the strawberries.
Spoon the batter onto the griddle 1/4 cup at a time. Cook the pancakes until set and thoroughly bubbly, about 3 minutes. Flip them with a spatula and cook until golden brown, about 2 minutes more. Serve with butter and maple syrup.