Preheat oven to 350°. Line a 9x13 pan with parchment paper, spray with cooking spray, and set aside.

Add the butter to a saucepan over medium heat. Melt the butter, while stirring. Once melted, it will foam, pop, and sizzle, this is normal. Keep stirring and do not step away from the stove, it can burn very quickly and then you will need to start over. 

The milk solids will separate and be on the bottom of the pan, and will get brown. The butter should smell toasted and nutty. It takes about 5 to 8 minutes for this to happen. 

Remove from the pan and pour the brown butter into a bowl to cool. If you do not remove it from the pan, it will continue to cook and can burn. 

Add brown sugar to a medium mixing bowl. Pour in browned butter and whisk until combined and the sugar begins to dissolve and is smooth. 

Whisk in eggs, one at a time. Add vanilla. 

Mix together flour, salt, and baking powder in a small bowl. Add to the butter mixture and mix until just combined and you cannot see streaks of flour. 

Add toasted pecans and chocolate chips and fold through. I reserve some for the top of the blondies. Pour batter into prepared pan. Add reserved pecans and chocolate chips and arrange on the top of the blondies. Sprinkle with sea salt. 

Bake for 23 to 25 minutes, being careful to not overbake.The center should be set and the edges golden brown. Cool in the pan, then remove from the pan and cut into squares.