Line a 12-hole muffin tin with paper cases. Using a freestanding mixer fitted with the beater attachment, or an electric hand mixer and bowl, cream together the butter and sugar until the mixture is light, pale and fluffy. Gradually add the eggs, beating well after each addition. Then pour in the milk, a little at a time, mixing lightly as you add it to the batter.
Sift together the flour, baking powder and salt and gently fold into the batter, being careful not to overwork the mixture as it could make the muffins tough. It’s fine if the batter seems a little lumpy. Use a large metal spoon to fold in the blueberries – try not to squish them!
Using a dessertspoon, fill the paper cases until two-thirds full. Bake for 18–20 mins, until the muffins are lightly golden brown, springy to the touch and a skewer inserted into the centre comes out clean.