Preheat oven to 375 degrees.
Mix flour, baking powder, salt and sugar.
Toss in blueberries (if using frozen, do not thaw first).
Mix all other ingredients until well combined.
Pour wet ingredients into dry, and stir gently until just combined.
Scoop into greased or lined muffin tins and sprinkle with cinnamon sugar if desired.
Bake for 18-22 minutes or until lightly browned.