1. Heat oven to 350 degrees . In a bowl, whisk together flour, cocoa, baking powder, baking soda and salt. In another bowl, beat butter, granulated sugar and brown sugar for 2 minutes, until fluffy. Beat in egg and vanilla extract until just combined. Pour in flour mixture and beat on low until just combined. Carefully fold in chocolate chips and chopped pretzels.
2. Drop tablespoonfuls of batter on baking sheets, spacing them about 2 inches apart. Press down lightly to flatten. Gently press a whole pretzel on top of each cookie.
3. Bake at 350 degrees for 11 minutes. Transfer to a wire rack to cool completely.