Ingredients: -
115 grams unsalted butter, softened to room temp,
200 grams granulated sugar,
2 large eggs, room temp,
2 tsp pure vanilla extract,
120 grams sour cream or plain yogurt room temp,
120 ml milk, room temp,
250 grams all-purpose flour, 
2 tsp baking powder,
1/2 tsp ground cinnamon,
1/2 tsp salt,
1 cup fresh or frozen blueberries,
METHOD: -
Preheat oven temperature to 210C. Line a 12-count muffin pan with cupcake liners and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl use a hand-held mixer, cream together the butter and sugar for 4-5 mins or until light and fluffy. Add the eggs and vanilla extract one at a time, mixing well after each addition, stopping to scrape down the sides of the bowl as needed. Mix in the sour cream and milk.
In a mixing bowl, whisk together the flour, baking powder, cinnamon, and salt. Add the dry ingredients to the wet ingredients and mix until just combined. Gently fold in the blueberries. 
Evenly distribute the batter between all 12 muffin liners, filling each one to the top. Bake at 210°C for 5 mins, then without opening the oven door, reduce the oven temperature to 190°C and continue baking for an additional 15-18 mins or until a toothpick inserted into the centre of the muffins comes out clean.
Remove from the oven and allow to cool in the pan for 2-3 mins, then carefully remove the muffins from the pan, and transfer to a wire rack to cool.