1. In a large mixing bowl, cream together the softened butter and both types of sugar until light and fluffy (about 2-3 minutes).
2. Beat in the two large eggs one at a time, mixing well after each addition. Stir in the vanilla extract until fully incorporated.
3. In a separate bowl, whisk together the flour, baking soda, and salt until thoroughly combined.
4. Gradually add the dry mixture to the wet mixture. Mix on low speed until just combined, being careful not to overmix the dough.
5. Gently fold in the pre-baked brownie pieces and chocolate chips, distributing them evenly throughout the mixture.
6. Drop rounded tablespoons of the dough onto parchment-lined baking sheets, leaving adequate space between each portion.
7. Place the sheets in a preheated oven at 375°F (190°C). Bake for 10-12 minutes, or until the edges are golden brown and the centers are slightly soft.
8. Let the cookies cool on the baking sheets for a few minutes, then transfer them to a wire rack to cool completely.