2 sticks unsalted butter, at room temperature
1 cup dark brown sugar, packed
1/2 cup granulated sugar
2 large eggs
1 teaspoon natural vanilla extract
2 1/4 cups all purpose flour
1 teaspoon salt
3/4 teaspoon baking soda
1/2 cup peanut butter chips
1/2 cup toffee chips
1/2 cup mini-marshmallows
2 cups imported semisweet chocolate chunks
Cream butter in an upright mixer until fluffy. Add dark brown and white sugar and mix until thoroughly blended with butter, scraping sides and bottom of bowl from time to time.
Add eggs, one at a time, and mix until thoroughly blended, scraping sides and bottom bowl from time to time. Add vanilla extract and mix at low speed to combine well.
In a separate bowl, mix flour, salt, and baking soda. Add flour mixture to butter/sugar mixture and mix at low speed, until thoroughly blended, scraping the sides and bottom of the bowl from time to time. Mix briefly at medium speed until completely combined.
Add peanut butter chips and mix on low speed until thoroughly combined. Add toffee chips and mix on low. Add mini-marshmallows and mix on low speed until thoroughly combined. Add chocolate chunks and mix on low. Refrigerate batter for a few hours or overnight until cold.
Preheat oven at 350 degrees (300 if using a conventional oven). Line baking sheet with parchment paper and drop heaping teaspoonfuls of batter 2 inches apart.
Bake for approximately 12 to 18 minutes, turning tray once during baking. Cookies are done when they are golden brown around edges and soft (not bubbly) on top. Let cool on wire rack.