In a large mixing bowl, whisk together the flour, cornstarch, baking soda, and salt.

In a separate bowl, whisk the melted butter with the brown sugar and granulated sugar until smooth and no lumps remain.

Add the egg, egg yolk, and vanilla extract, then whisk until fully combined.

Pour the wet ingredients into the dry ingredients and mix with a spatula until just combined.

Fold in the chopped white chocolate.

Gently fold in the raspberries, taking care not to overmix.

Scoop and roll the dough into evenly sized balls and place them on a parchment-lined baking tray.

Cover and refrigerate for 30 minutes, then let the dough sit at room temperature for 5 minutes before baking.

Preheat the oven to 325°F (160°C) and line two baking sheets with parchment paper.

Arrange the cookie dough balls about 2 inches apart and gently flatten each one slightly with your hand.

Bake the White Chocolate Raspberry Cookies for 10–12 minutes, or until the edges are set and the centers still appear slightly soft.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack. For perfectly round cookies, gently tap the baking sheet on the counter and shape the cookies with a large round cutter while they're still warm.