Preheat oven to 350ºF. Spray a 9x13-inch baking pan with nonstick cooking spray and set aside.
In a medium bowl, whisk together flour, salt, and baking soda. Set aside.
In the bowl of a stand mixer, mix melted butter and sugars together until combined. Add eggs and vanilla and mix until smooth. Slowly add dry ingredients and mix on low, just until combined. Stir in white chocolate chips and pretzel pieces.
Pour blondie dough into the prepared pan, smoothing the top with the spatula. Place pretzels on top of bars, forming rows. Sprinkle blondies lightly with sea salt.
Bake blondies for 28–30 minutes or until the top of the blondies are light golden brown and the edges start to pull away from the pan. Remove from oven and cool on a wire rack to room temperature. Cut bars into squares and serve.