Preheat the oven to 350 degrees F. Grease a 9 x 13 baking pan and line with parchment paper.
In a bowl combine the flour and baking powder.
Using a stand mixer, beat the butter and brown sugar until light and fluffy.
Add the eggs one at a time and mix well after each addition.
Scrape down the bowl after each egg is added.
Pour in the vanilla and mix.
Turn the mixer to low speed and gradually add the flour.
Once the flour is mixed in add both the butterscotch chips and chocolate chips, 1 cup of each.
Add the pecans and transfer the batter to the prepared pan spreading it out evenly.
Bake in the oven for 35 minutes.
Let cool before drizzling with both kinds of melted chocolate.
Melt the chocolate and butterscotch in the microwave and drizzle over the blondies.
Sprinkle lightly with sea salt flakes if desired
Slice and serve.