Arrange a single layer of Nutter Butter cookies in the bottom of a 9×13-inch baking dish. (Save the remaining Nutter Butters for the topping.): The moment you place those cookies the base takes shape visually and structurally. You should hear a faint snap as each cookie meets the pan and feel their firmness under your fingers, which ensures a crunchy foundation that will hold up to the wet layers. Make sure cookies sit edge to edge with minimal gaps so the cream cheese layer can rest evenly. A common mistake is leaving large gaps between cookies, which leads to weak spots in the finished bars, so press them gently into a single even layer.
In a large bowl, use a hand-held electric mixer to mix together cream cheese and powdered sugar. Then beat in 1 cup of Cool Whip.: As you whip, watch the texture transform from lumpy to silky, and notice the sweet, tangy aroma lift from the bowl. The goal is a satiny, lump free mixture so the sugar fully dissolves into the softened cream cheese . Beat at medium speed until smooth, then incorporate 1 cup of Cool Whip until light and airy. If you under whip, the layer will feel dense and heavy; over whip and it can lose body or become too loose, so stop once it looks smooth and holds gentle peaks.
Spread cream cheese mixture over Nutter Butters and then refrigerate for at least 20 minutes.: When spreading, run a rubber spatula across the surface to create an even cushion, and you will feel slight resistance as the mix meets the textured cookie tops. Chilling firms this layer, preventing the next wet layer from seeping into the cookies. If you skip chilling, the cookie base can become soggy and the layers may blend together, so give it those twenty minutes to set properly.
Either rinse out the bowl or use a new bowl to beat together vanilla pudding mix and whole milk. Continue to beat until it starts to thicken. Then beat in peanut butter and 1 cup of Cool Whip.: As you whisk, the pudding will thicken and release a sweet, creamy perfume. Beat until it starts to set, then add 1 cup of creamy peanut butter and 1 cup of Cool Whip , beating until smooth. The peanut butter should meld fully into the pudding, creating a glossy, peanut scented mass. A sign it's ready is when the mixture holds some body and does not run off the spoon. Avoid under mixing, which leaves pockets of dry powder, and over mixing, which can make the texture pasty.
Spread pudding mixture over cream cheese layer. Refrigerate at least 20 minutes.: Smooth the peanut butter pudding with a spatula, watching the color shift to a uniform, light brown sheen. The sound here is silence as the paddle glides, and the surface should look satiny and slightly thick. Refrigerate again for at least 20 minutes so this dense layer firms, locking in the layers. If you skip chilling the pudding, assembly will be messier and slicing will be difficult, so patience pays off.
Spread remaining Cool Whip on top.: Apply the remaining whipped topping in gentle sweeping motions to create a cloud like cap. The visual cue is a soft white finish that hides the layer below while still showing a hint of strata at the edge. Keep the strokes light to avoid compressing the pudding layer underneath. The common error is over smoothing, which can break the pudding finish and create an uneven top.
For the topping, place the peanut butter in a microwave-safe bowl and microwave for 10 seconds. Transfer to a ziplock bag. Snip the corner and drizzle on top of the lush.: After heating, the peanut butter will smell warm and nutty and become runny enough to pipe. Transfer it to a ziplock bag, snip a small corner, and drizzle across the surface to create thin glossy ribbons. The quick warm up makes it fluid while preserving flavor. Be careful not to overheat, which can make it scorch and taste bitter.
Sprinkle the chopped Butterfinger on top. Chop the remaining Nutter Butter cookies and arrange them on top.: The act of sprinkling adds a crisp, brittle sound and a sparkly visual contrast. Distribute the chopped candy and cookie bits evenly so every slice gets some crunch. This step transforms texture and appearance, offering caramelized sugar notes and cookie fragments that play against the creamy layers. Avoid piling too much in one area which leads to uneven bites and a top that slides when cut.
Refrigerate for at least 2 hours before serving.: This final chill is when flavors harmonize and layers firm to a sliceable consistency. You will notice the pan becoming cool to the touch and the top setting into a slightly more matte finish. Two hours ensures the pudding and cream cheese layers stabilize for clean serving. Serving too soon is the usual pitfall here, resulting in a runny cut and messy presentation, so give it the rest time it needs.