Cut the butter into cubes and leave at room temperature to soften.
Preheat an oven to 180ºC.
Line the muffin tin with paper muffin cups.
Fit the K beater to the machine.
Sift Ingredients 1 (flour, baking powder, salt) into a clean medium bowl.
Attach the Mixer bowl to the machine and fit the splash guard.
Add Ingredients 2 (butter, sugar) into the Mixer bowl.
Start the speed on Min and gradually increase speed.
Mix on speed Max for about 1 minute until light and fluffy.
Add Ingredients 3 (eggs) into the Mixer bowl.
Mix on speed Max for about 30 seconds until combined.
With the machine running, add contents of the medium bowl into the Mixer bowl.
Mix on speed 4 for about 1 minute until combined.
Add Ingredients 4 (milk) to the bowl.
Mix on speed 2 for about 1 minute until thickened.
Add Ingredients 5 (blueberries) into the Mixer bowl.
Mix on speed 3 for 30 seconds until combined.
Transfer the mixture into the paper muffin cups.
Bake for 25 minutes at 180°C until a skewer tests clean.