In a saucepan, melt butter over medium heat, stirring occasionally until butter has browned and has a nutty scent. Remove from heat, set aside and allow to cool completely.
In a large bowl, sift together all-purpose flour, baking soda and salt. Set aside.
Once brown butter has completely cooled, cream butter and sugars in a large bowl with an electric mixer. Add eggs and vanilla. Beat again with an electric mixer until smooth.
Add the flour mixture to the butter mixture and beat until combined.
Fold in peanut butter chips, semi-sweet chocolate chips and crushed pretzels. Cover the batter and chill for 2 hours.
Once cookie dough has been chilled, preheat over to 350ºF. Line a baking sheet with parchment paper. Scoop dough into 2" balls, placed approx. 2" apart. Add extra chocolate chips and pretzel pieces to the top.
Bake for 12 minutes, or until the edges are golden brown.
Allow to cool and enjoy a chewy cookie!