Preheat the oven to 350°F (180°C) and line two baking sheets with parchment paper. This helps the cookies bake evenly and release easily.
Beat the softened butter and sugar until the mixture is light, fluffy, and pale, about 2–3 minutes.
Mix in the egg, egg yolk, and vanilla extract until smooth and fully combined.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Gradually mix the dry ingredients into the wet ingredients just until no dry flour remains.
Gently fold in the frozen raspberries and white chocolate chips using a spatula. Mix lightly so some raspberry pieces stay whole and create beautiful pink swirls.
Scoop about 2 tablespoons of dough for each cookie and place on a tray. Chill for 30 minutes in the refrigerator or 15 minutes in the freezer.
Arrange the chilled dough balls 2 inches apart on the prepared baking sheets. Bake for 10–12 minutes until the edges are lightly golden and the centers still look slightly soft.
Let the cookies cool on the baking sheet for 10 minutes before transferring them to a cooling rack. They will continue setting as they cool.