Preheat oven to 350°F (175°C). Line a baking sheet with parchment or a silicone mat.

In a large bowl, beat the softened butter and cream cheese until smooth and creamy (about 1–2 minutes).

Add the sugar and beat until light. Mix in the egg and vanilla until combined.

In a separate bowl, whisk together the flour, baking powder, and salt.

Gradually fold the dry ingredients into the wet mixture until just combined. Avoid overmixing.

Gently fold in the blueberries and white chocolate chips (if using). Make sure to fold in frozen blueberries straight from the freezer.

Using a tablespoon or small cookie scoop, drop rounded portions of dough onto the prepared baking sheet, spacing them about 2 inches apart.

Bake for 12–14 minutes, or until the edges are set and the centers look slightly puffed. Avoid overbaking.

Cool on the baking sheet for 5 minutes, then transfer to a wire rack to finish cooling.