Mix flour, sugar, and baking powder in a bowl, then stir in strawberries with a wooden spoon.
Mix eggs, buttermilk, and melted butter in another bowl.
Stir the liquid ingredients into the dry ingredients until smooth.
Divide 3⁄4 of the batter evenly between the paper cases to three-quarter fill.
Press in the centre of each muffin using a spoon to make a well. Fill each well with a teaspoon of chilled custard, then gently spoon the rest of the muffin mix over the custard.
Bake for 30 - 35 minutes until golden and oozing custard. Sprinkle each with a little caster sugar while still warm.
Serve immediately or store in an airtight container.
