To a medium bowl, add flour, baking soda, and salt. Whisk to combine; set aside.
To the bowl of a stand mixer fitted with the paddle attachment (or use a large mixing bowl and electric hand mixer), add softened butter and both sugars. Mix on High speed until fluffy and creamy, about 2 minutes.
Use a spatula to scrape down the insides of the bowl. Add the egg and vanilla extract, and mix on Medium speed until smooth.
With the mixer set to Low speed, gradually incorporate the flour mixture, beating until just barely combined. Be careful not to over mix.
Using a mixing spoon, stir in the Snickers, peanuts, chocolate chips, and chocolate chunks by hand, distributing them evenly throughout the dough.
Cover the bowl with plastic wrap and place in refrigerator for 30 minutes.
When dough is cold, preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Using a 1-inch cookie scoop, drop portions of dough onto the prepared baking sheet, spacing them 2 inches apart to allow for spreading.
Bake cookies in preheated oven for 12-15 minutes, or until the edges are golden brown and the centers still appear slightly underdone.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes. Then, use a spatula to transfer them to a wire rack to cool completely.