Line a 12 tin muffin tray with muffin cases. Cream the butter and sugar together in a large mixing bowl until pale and fluffy. Slowly add the beaten eggs, whisking constantly at the same time until incorporated.
Sift in the flour and baking powder, mix well and chill for an hour at least. Preheat the oven to 190°C when ready to bake, then spoon the mixture evenly into the muffin cases.
Stud each muffin with 5-6 blueberries then bake for 18-22 minutes until golden and risen. Remove when ready and allow to cool a little before turning out onto a wire rack. Serve warm or cold.