Preheat oven 200 degree c. Take a muffin pan, line with cupcake cases.
Take butter, sugar, cinnamon, flour and mix well. Set aside.
Heat butter, sugar, egg, in a bowl and mix well.
Add in milk, vanilla and mix well.
Add in flour, baking powder, salt and fold gently.
Add in blueberries and fold gently.
Spoon the muffin batter in cupcake cases.
Top with streusal topping.
Bake for 20 to 25 mins.
Remove and serve warm.