Preheat the oven to 400℉/218℃. Line a muffin tin with muffin liners and set aside.
In a bowl, add the flour, baking soda, baking powder, cinnamon, cornstarch, and salt. Stir to combine and set aside.
2 1/2 cups all-purpose flour, 2 1/2 tsp baking powder, 1 tsp baking soda, 1/4 tsp salt, 1 tsp cornstarch, 1/4 tsp cinnamon
In a large bowl, add the melted butter, eggs, vanilla, white sugar, yogurt, and oil. Whisk to combine for 2-3 minutes and set aside.
1/3 cup oil, 1/4 cup unsalted butter, 2 large eggs, 1 cup yogurt, 3/4 cups white sugar, 1 tbsp vanilla
Combine the dry and wet ingredients until a soft muffin batter forms. Do not over-mix!
*If your blackberries and raspberries are large, slice into smaller pieces* Into the bowl with the mixed berries, add 1 tbsp of flour and coat the berries in the flour. Then add them into the muffin batter and mix a few times.
2 cups mixed fresh berries*
Scoop the muffin batter into the liners. Add extra berries and sprinkle some white sugar on top (optional).
Place the muffins in the oven at 400℉ and then immediately reduce the temperature to 375℉. Bake the muffins for 20-25 minutes or until a toothpick inserted comes out clean.
Allow the muffins to cool, and enjoy!