Preheat the oven to 375°F (190°C) and line a muffin tin with paper liners.
In a bowl, whisk together flour, sugar, baking powder, and salt.
Add milk, vegetable oil or melted butter, egg, and vanilla extract to the dry ingredients and mix until just combined; do not overmix.
In a separate bowl, beat softened cream cheese, sugar, and vanilla extract until smooth and creamy.
Fill each muffin liner halfway with batter, then add a spoonful of cheesecake filling in the center.
Cover the cheesecake filling with more muffin batter.
Sprinkle the mixed berries on top of each muffin and gently press them in.
Optionally, sprinkle 2 tablespoons sugar over the berries for a crunchy topping.
Bake for 20 to 25 minutes until the muffins are golden and set.
Allow muffins to cool slightly before serving.