Heat oven to 350F. Grease and flour 9 x 13 pan, or alternatively line with baking paper. Set aside
In the bowl of your stand mixer, combine melted butter, brown sugar, eggs, and vanilla. Scrape down the sides of the bowl with a spatula.
Add in flour, baking powder, and salt. Mix to combine. While mixer is on low, add in pecans and chocolate chips.
Pour into pan and using spatula or your hands dusted with a little bit of flour, spread the batter evenly.
Bake 30-35 minutes, or until lightly brown around the edges and the center cooked through. Cool in pan for 10-15 minutes. Cut into 24 squares.