Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.

In a large bowl, beat the softened cream cheese, softened butter, granulated sugar, and brown sugar until smooth and creamy.

Add the egg and vanilla extract. Beat until the mixture is even and glossy.

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

Gradually add the dry ingredients to the wet mixture. Stir with a spatula until just combined. Do not overmix.

Gently fold in fresh blueberries if using.

Drop rounded scoops of dough onto the prepared sheet, spacing them about 2 inches apart.

Press a small indentation into the center of each cookie with the back of a teaspoon.

Fill each well with about a teaspoon of blueberry jam.

Bake for 12 to 15 minutes, until the edges are lightly golden and the centers look set.

Cool the cookies on the baking sheet for 3 to 5 minutes, then transfer them to a wire rack to cool completely.

Dust with powdered sugar before serving if desired.