Preheat your oven to 400°F (200°C) and line two baking sheets with parchment paper.

Cream 1 cup of softened unsalted butter with 3/4 cup light brown sugar and 3/4 cup granulated sugar until light and fluffy, about 2-3 minutes.

Add 2 large eggs, one at a time, mixing well after each. Stir in 2 teaspoons of vanilla extract until smooth.

In a separate bowl, whisk 2 1/4 cups of all-purpose flour, 1 teaspoon baking soda, and 1/2 teaspoon salt together.

Gradually add the dry ingredients to the wet mixture, mixing on low speed until just combined.

Fold in 1 cup of semi-sweet chocolate chunks, 1 cup of milk chocolate chunks, and 1 cup of chopped walnuts (if using).

Scoop large portions of cookie dough (about 6 ounces each) onto the prepared baking sheets, spacing them 2-3 inches apart.

Bake cookies for 13-15 minutes until the edges are golden brown but the centers are slightly underbaked.

Let cookies cool on the baking sheet for at least 10 minutes before transferring to a wire rack to cool completely.