1. Preheat the oven to 350°F. Spray a 9x13 pan with cooking spray.
2. In a bowl, whisk the flour, baking soda and salt. Using a mixer, beat the butter and both sugars at medium speed until light and fluffy, about 1 minute. Beat in the eggs and the vanilla extract. On low speed, beat in the dry ingredients just until incorporated. Stir in the chocolate chips and pretzel pieces.
3. Spread the batter evenly in the pan and press it down evenly with a spatula. Bake for 30 minutes, until golden brown. Transfer the pan to a rack and cool completely.
4. In separate sandwich size baggies, melt the chocolate chips and peanut butter. Cut off a small corner on each bag and drizzle the chocolate and peanut butter over the top of the bars. Sprinkle the extra crushed pretzels on top. Let set and then cut into squares.