Preheat oven to 350°F (175°C), line pan with parchment, grease lightly.
Whisk melted butter and both sugars until smooth.
Add eggs one at a time, then stir in vanilla.
Whisk flour, baking powder, salt separately, fold into wet mix.
Stir in chocolate chips and nuts, spread batter in pan.
Sprinkle reserved chips on top.
Bake 25–30 minutes until edges set, center slightly underbaked.
Cool in pan, lift with parchment, cut into squares.