• Preheat the oven to 350°F (180°C). Line a 12-hole muffin pan with muffin paper liners. Use cooking spray to oil the liners. Set aside.
• In a large mixing bowl, prepare the homemade buttermilk mixture. Whisk apple cider vinegar with milk. Set aside for 10 minutes until it curdles.
• In another large mixing bowl, whisk dry ingredients: cinnamon, all-purpose flour, sugar, salt, and baking powder.
• Add to the oil and vanilla extract to the bowl with the buttermilk. Stir to evenly combine.
• Stir the dry ingredients into the wet ingredients until the batter is smooth. Don't over-stir the batter to avoid tough blueberry muffins.
• In a small bowl, quickly stir the blueberries with cornstarch until well coated, then fold them in the muffin batter.
• Gently stir the blueberries in the batter.
• Use a cookie scoop to fill the muffin pan evenly.
• Bake the muffins at 350°F (180°C) for 25-30 minutes or until they are golden brown.
• After 20 minutes, insert a toothpick in the center of one muffin. If wet, keep baking.
• Cool down at room temperature for 5 minutes in the muffin pan, then on a wire rack for 1 hour or until safe to handle by hand.

Storage

• Store in a cookie box or airtight container in the fridge for up to 4 days.
• You can freeze muffins in zip-lock bags for up to 1 month. Thaw on the benchtop at room temperature the day before.