Peanut Butter Mud Bars

Ingredients

• 1 cup all-purpose flour
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 1/2 cup unsalted butter, softened
• 1 cup firmly packed light brown sugar
• 1/2 cup creamy peanut butter
• 1 large egg, at room temperature
• 1 teaspoon vanilla extract
• 3/4 cup + 2 tablespoons chocolate chips, divided
• 1/4 cup + 2 tablespoons white chocolate chips (or vanilla chips), divided
• 1/2 cup + 2 tablespoons peanut butter chips, divided
• 1/4 cup coarsely chopped pecans