Preheat the oven to 160˚C fan /180˚C / 350˚F.
Line 2-3 baking sheets with baking paper / parchment paper
Roughly crush the pretzels (see tips below for how to crush them), then tip on to a plate and leave to one side.
Sift the flour, baking soda, baking powder and salt into a medium bowl.
Using a stand mixer or hand-held beaters, cream the butter with the brown sugar, granulated sugar and vanilla until light and fluffy.
Whisk in the egg, then add the dry ingredients and mix together with a large spoon or spatula until just combined.
Fold in the chocolate chips until just combined.
Using a cookie scoop or tablespoon, scoop balls of dough then lightly roll in the chopped pretzel pieces to coat all of the cookie dough in pretzel pieces.
Place the balls onto the lined baking sheets, allowing room in between for them to spread.
Place in the preheated oven and bake for 10-12 minutes, until the edges are light golden brown.
Cool the cookies on the baking sheet for 5-10 minutes, then carefully transfer them to a wire rack and leave to cool completely.
Store cookies in an airtight container at room temperature for up to 1 week.