Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until well combined.

In another bowl, crack the egg, add milk and vanilla extract, and whisk until smooth and frothy.

Pour the wet ingredients into the dry mixture and gently stir until just combined.

Cut the softened cream cheese into small chunks and fold it gently into the muffin batter.

Gently fold your mixed berries into the batter.

Spoon the batter into the prepared muffin cups, filling each about two-thirds full.

If using, mix together the flour, sugar, and cold butter in a separate bowl until crumbly and sprinkle over each muffin.

Place the muffin tin in the preheated oven and bake for 18-20 minutes.

Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack.