Melt the margarine. Crack the egg into a bowl. When the margarine has cooled, add it to the bowl along with the sugar and mix.
Mix the dry ingredients separately and then add to the egg mixture. Add the milk and mix.
Finally, fold the frozen blueberries carefully into the batter. Transfer the batter into a muffin tray using two spoons (one to scoop out and pour the batter, one to scrape the batter off the other spoon).
Bake at 225 °C for 10–15 minutes.