Start by preheating your oven to 350°F (175°C) and line your baking tray with parchment paper. This prevents sticking and ensures even baking. I always do this first so everything is ready once the dough is mixed.
In a large bowl, combine melted butter with brown sugar and granulated sugar. Mix until smooth and glossy. This step is important because properly blended sugar creates that signature chewy texture.
Add the egg, extra yolk, and vanilla extract into the mixture. Stir until everything is fully incorporated. The mixture should look creamy and slightly thick at this stage.
In a separate bowl, whisk together flour, baking soda, and salt. Gradually add this to the wet mixture. Mix gently until no flour streaks remain, but avoid overmixing to keep cookies soft.
Gently fold in white chocolate chips first, then add frozen raspberries. Work quickly because the raspberries may start to thaw. This ensures even distribution without making the dough too wet.
Use a cookie scoop to form evenly sized dough balls. Place them about 2 inches apart on the baking tray. This spacing allows cookies to spread properly without sticking together.
Bake for about 12 minutes or until the edges turn golden and centers look slightly underdone. This ensures a soft, gooey middle. Let them cool on the tray before serving.