Yield: about 16 4-inch or fifty 2 ½-inch cookies

Position a rack in the center of the oven. Preheat the oven to 350°F. Grease cookie sheets or cover with parchment paper or greased aluminum foil.

Beat on medium speed until very fluffy and well blended:

14 tablespoons (1 3/4 sticks) unsalted butter, softened
2 cups sugar
1/2 cup packed dark brown sugar
Beat in 1 at a time until well combined:
3 large eggs
Mix in:
1 1/2 cups creamy peanut butter
3/4 teaspoon vanilla
Stir in until just combined:
2 1/4 cups all-purpose flour
3/4 teaspoon baking soda
1/4 teaspoon salt

Add and stir until mixed:

1 cup coarsely chopped bittersweet or semisweet chocolate
3/4 cup unsalted shelled peanuts
Using 1/3 cup for each monster, drop the dough onto the sheets, spacing about 3 inches apart. Bake, 1 sheet at a time, until the cookies are golden brown, 20 minutes. For regular-sized cookies, drop by heaping measuring teaspoonfuls 1 1/2 inches apart and bake for 15 minutes. Remove the sheet to a rack and let stand until the cookies firm slightly. Transfer the cookies to racks to cool