Preheat the oven to 175℃ (350℉).
Grease a muffin tin or line with muffin cases.
In a bowl or stand mixer, combine the flour, baking powder, cinnamon, nutmeg, salt, and sugar.
Add the chopped butter and, using either your hands or a stand mixer with the paddle attachment, rub the ingredients together. See here for more information. The mixture is ready when no large pieces of butter remain.
Add the eggs one at a time, followed by the vanilla, mixing well after each addition.
Gradually add the milk until a thick batter comes together.
Gently fold most of the blueberries into the batter, reserving the rest for topping.
Divide the batter between six muffin holes/cases, filling them right to the top. For smaller muffins, divide the mixture between eight.
Press three or four of the reserved blueberries into the top of each muffin. Sprinkle with a little brown sugar, if desired.
Bake in the lower three-quarters of the oven for about 35–40 minutes, or until the tops are golden and a skewer inserted into the centre comes out clean (start checking at the 30-minute mark).
Let the muffins cool slightly and enjoy warm. Freeze any leftovers for later. Enjoy!