Cooking spray
(375 g.) packed light brown sugar
(1 1/2 sticks) unsalted butter, melted
(180 g.) all-natural chunky peanut butter
baking powder
pure vanilla extract
kosher salt
large eggs, room temperature
(240 g.) all-purpose flour
(3.75 oz.) mini pretzels, divided
(6 oz.) butterscotch chips, divided