Preheat nothing. Line an 8x8- or 9x9-inch pan with foil, leaving some foil overhang for lifting the fudge out later, and butter the foil.

Combine 3 cups sugar, 2/3 cup evaporated milk, and 3/4 cup butter in a heavy-bottomed saucepan.

Place the saucepan over medium heat and stir continuously until the sugar dissolves and the mixture comes to a full boil. Use a heavy spoon or heatproof spatula and be careful — the mixture is very hot.

Clip a candy thermometer to the pan and continue cooking, stirring frequently, until the mixture reaches the soft-ball stage (234–240°F / 112–116°C). If you do not have a thermometer, proceed with caution and look for the syrup to thicken and form a soft ball in cold water.

Immediately remove the pan from the heat.

Add the 10 oz coarsely chopped Reese’s peanut butter chips to the hot mixture and stir until the chips are fully melted and the mixture is smooth. Chopped chips will melt faster.

Stir in the entire 7 oz jar of marshmallow creme until the mixture is fully combined and smooth.

Stir in 1 tsp vanilla extract and the 15 coarsely chopped Nutter Butter cookies until evenly distributed.

Pour the hot fudge mixture into the prepared pan and use a spatula to spread and level the top.

Let the fudge cool completely at room temperature until firm. Use the foil overhang to lift the fudge from the pan, then cut into squares.

Store leftovers in an airtight container.