These are fantastic and come from a book I got in New York - "Bubby's Brunch Cookbook".
Cream the butter and the sugar together for about 3 minutes at a high speed - must go creamy. If in doubt, go longer.
Add the eggs one at a time, beating after you add each one.
Pour in the sour cream and the milk and whiz until all combined.
Chuck in the flour and whizz slowly. It will be quite a thick batter at this stage. Fold in the blueberries.
Pop in some cupcake paper things and cook at 180 degrees for 20 minutes. Leave to cool for 5 minutes in the pan and then take them out and let them cool on a rack/plate.
My dad does not like blueberries (useless) so he got a muffin with bits of banana instead - try it if you are as mad as he is.