1-First Step: Preheat and Prep Set oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone mats. This prevents sticking and ensures even baking. Soften butter to room temperature, and crush Oreos into small chunks using a food processor or zip bag and rolling pin. Measure all ingredients for smooth sailing.

2-Second Step: Mix Wet Ingredients In a large bowl, beat 1/2 cup softened unsalted butter, 2 large eggs, and 1 tsp vanilla extract. Use a hand mixer on medium speed for 2 minutes until creamy and light. This builds the base emulsion, trapping air for tender cookies. Room-temp eggs mix better, avoiding lumps.

3-Third Step: Incorporate Cake Mix Gradually add the 1 box (15.25 oz) vanilla or funfetti cake mix to the wet mixture. Stir on low until a thick dough forms, about 1-2 minutes. Scrape sides to blend fully. The dough will be sticky, like edible cake batter, but holds shape when scooped.

4-Fourth Step: Fold in Oreos Gently fold in 1 cup crushed Oreo cookies with a spatula. Avoid overmixing to keep chunks intact for crunch. This step adds the oreo dessert magic. If dough seems too wet, chill 10 minutes.

5-Fifth Step: Scoop and Bake Drop 1.5 tbsp dough scoops (or use a cookie scoop) onto sheets, spacing 2 inches apart. Do not flatten; they spread naturally. Bake 10-12 minutes until edges turn golden. Centers stay soft for that fluff cookies feel. Rotate sheets halfway for even heat.

6-Sixth Step: Cool Slightly Let cookies cool on sheets 5 minutes. They firm up here. Transfer to a wire rack.

7-Final Step: Add Fluff and Finish Microwave 1 cup marshmallow fluff 10 seconds to loosen. Swirl 1 tsp onto each warm cookie. Top with sprinkles right away. Cool fully before storing. Enjoy the gooey melt!