Preheat the oven to 350°F. Line 2 baking sheets with parchment paper.
Use a whisk to sift together the all-purpose flour, baking powder, baking soda and salt in a medium bowl. Set aside.
In the large bowl of a stand mixer cream together the softened butter, light brown sugar, granulated sugar, peanut butter and vanilla extract. Beat for 2-3 minutes until smooth, fluffy and light beige in color.
Add the eggs one at a time beating well after each addition. Stop and scrape the bowl periodically, so all of the ingredients fully combine.
Add the dry flour mixture gradually while beating on low speed, until all of the dry ingredients have been added. Stop periodically to scrape the sides of the bowl.
After all of the dry ingredients have been added, increase the speed of the mixer and beat for 30-60 seconds.
Use a large non-stick spatula or spoon to stir the cubed Snickers bars, pretzel pieces, peanuts, and chocolate chips into the batter by hand. The batter will be stiff. Mix until the ingredients are evenly distributed.
Use a 1 1/2 Tbsp ice cream scoop or cookie scoop to separate the dough into round balls.
Place the dough balls at least 3-inches apart on the prepared sheet pans to allow room for spreading.
Press the centers to flatten slightly for even baking. (A bigger scoop will make jumbo cookies, adjust baking time accordingly.)
Bake for 18 minutes rotating the pans if needed, until lightly golden brown.
Cool on the cookie sheet for 3 minutes, then remove to a wire rack to cool completely.