Preheat oven to 425 degrees F. Combine the flour, 1/4 cup of the sugar, baking powder, and salt in a large bowl. Stir in milk, egg and butter, stirring only enough to dampen all the flour; the batter should not be smooth.
Spoon into buttered muffin cups, filling each about two-thirds full. Press strawberry slices into batter, pointed side up. Sprinkle each muffin with 1 teaspoon of the sugar.