Preheat oven to 350℉. Line 2 baking sheets with parchment paper.
Use a mixer to combine the 1 cup of softened butter, ⅔ cups light brown sugar, and 1 cup of white granular sugar. Mix on low for 3-4 minutes.
Next, add in the 2 eggs and 2 teaspoons of vanilla extract. Mix for 1 more minute.
In a separate large bowl, add 2 cups of flour, ⅔ cups of cocoa powder, 1 teaspoon of baking soda, and ¼ teaspoon of salt. Use a handheld whisk to combine.
Then, add the bowl of dry ingredients to the bowl of wet mixture and mix on low speed until all ingredients are well combined. Set aside.
In a separate medium sized bowl, combine ½ cup semi sweet chocolate chip morsels, ½ cup peanut butter morsels, ½ cup white chocolate chips, and ½ cup Reese's Pieces. Using a spoon, stir until combined.
Gently fold in ¾ of the candies into the cookie batter, setting the rest aside until after the cookies are done.
Scoop 2 Tablespoons of the cookie dough and shape it into a ball by rolling the dough between the palms of your hand. Put each ball on the cookie sheets, about 2 inches apart. Note: The cookie dough is going to be more on the soft side. Using your hand, gently press the ball of dough until flat. If desired, gently press additional pieces of candy into each cookie. This makes the cookies look extra appealing! Put the cookie sheets in the oven and bake for 14 minutes.Important Note: When you remove the cookies from the oven, they are going to be soft and may not appear to be done. Be assured they are done and will firm up as they cool. About 10 minutes after removing the cookies from the oven, transfer each cookie from the cookie sheet to a cooling rack. Allow them to completely cool.
Store in an airtight container.