1.Preheat oven to 180°C/350°F. Grease two 12-hole(⅓-cup/80ml) muffin pans.
2.Place butter and milk in small saucepan; stir over low heat until butter melts. Cool to room temperature.
3.Beat eggs in small bowl with electric mixer until thick and creamy. Gradually add sugar, beating until dissolved between additions; stir in banana. Fold in flour and cooled butter mixture, in 2 batches. Divide mixture into pan holes.
4.Bake cakes 10 minutes. Remove pan from oven; press frozen blueberries into tops of cakes. Bake a further 10 minutes. Turn cakes, top-side up, onto wire rack to cool. Dust with sifted icing sugar, if you like.
Cakes can be stored in an airtight container for up to 3 days. Cakes are suitable to freeze for up to 1 month.Note