Preheat oven to 350 degrees. Coat a 9 x 13 inch baking pan with cooking spray and parchment paper.
In a large bowl microwave safe bowl, melt butter on high for about a minute. Mix in the brown sugar, eggs, and vanilla and stir to combine. Stir in the flour, baking powder, and salt until well combined. Fold in the chips and pecans. Pour the mixture into the pan using a rubber spatula to spread.
Bake for 28-30 minutes, until toothpick inserted in middle comes out clean. (If the edges start to brown, cover the top of the pan with a loose piece of foil.) Cool in pan on a wire rack then transfer to refrigerator to cool completely before removing from pan.
Notes
These are great to make ahead too! Just cool completely and store in an airtight container in the refrigerator for up to a week.