Place a rack in the center of the oven and preheat to 375°F. Coat an 8×10-inch or similar baking dish with nonstick spray (you can go all the way up to 9×13, the dip will just be thinner and heat more quickly).: When you slide the dish into the oven you should smell a faint warmth in the air as the elements come up, which primes the surface for even browning. Preheating is crucial so the dip heats evenly from the start, helping the top melt and bubble rather than cook unevenly. A common mistake is to skip preheating, which leads to longer bake times and a soggy center. Check that the rack sits in the middle for balanced heat circulation, and ensure your oven temperature is accurate with a reliable oven thermometer.
In a large bowl, stir together the cream cheese, Buffalo sauce, yogurt, cottage cheese, garlic powder, and onion powder. Fold in the chicken, mozzarella, and 1/4 cup of the green onions.: The scent of the cooking spray will be faint, and you will notice the glossy surface of the dish which prevents sticking. Using the right sized dish affects texture, thinner layers will heat and brown faster while thicker layers stay creamier. Avoid using a dish that is too shallow, which can over crisp the edges before the center heats through. If you are unsure about size, err on the slightly deeper dish to retain moisture and even heat penetration.
Spread the dip in an even layer in the baking dish. Top with the cheddar.: As you mix, you will hear the soft scraping of the spoon and see the ingredients combine into a smooth, slightly orange tinted batter. This step develops the creamy base and evenly distributes the spice so each bite is consistent. If the cream cheese is not fully softened, lumps will remain, so ensure it is pliable before stirring. Over mixing is less harmful than under mixing here, but take care not to create an overly thin mixture by forcing it too aggressively.
Bake the Buffalo chicken dip until hot and bubbly, 20 to 25 minutes. Let cool a few minutes, then serve with dippers of choice.: Folding lets you integrate the chunks of warm or cold chicken and cheese without breaking down the textures, so you retain tender pieces and melty pockets. You should see strands of chicken coated in the creamy sauce and small flecks of green from the onions, which adds freshness. A common error is to stir vigorously, which can shred the chicken too finely and make the dip paste like. Use a gentle folding motion to keep the components distinct.
Spread the dip in an even layer in the baking dish: As you smooth it out, notice the glossy surface and slight resistance from the thicker spots, which indicates areas that might take longer to heat. An even layer ensures uniform heating and predictable bubbling across the surface. If you leave high peaks they can brown faster and dry out; take a spatula to level the mixture so it cooks consistently. Avoid pressing down hard which can compact the mixture and change the texture.
Top with the cheddar: The cheddar will sit on the surface and begin to melt into a golden blanket that browns attractively in the oven. Watch for color change to judge doneness, since melted cheese is both visual and aromatic, releasing a toasty scent as it starts to brown. Using an overly sharp cheddar can overpower the Buffalo tang, so choose a balanced cheese. One mistake is to add cheese too late or too early; add it before baking for a melded top, or only at the end if you prefer a distinct melted layer.
Bake the Buffalo chicken dip until hot and bubbly, 20 to 25 minutes: During baking you will hear faint bubbling and see steam rise at the edges, a clear sign the interior is piping hot. The top should be lightly golden and you may notice small oil glints from the cheese, which is normal and adds flavor. If the center seems cool after the suggested time, continue baking in short increments rather than drastically increasing temperature, which can char the top. Avoid opening the oven repeatedly, which causes heat loss and extends cooking time.
Let cool a few minutes, then serve with dippers of choice: Cooling lets the dip settle so scoops hold shape, and you will feel the warmth when you approach it, releasing savory steam. Serving too hot can cause the dip to run off dippers, while too cool it will firm up and lose that melty appeal. A common mistake is to serve immediately and burn mouths, so allow a few minutes for the texture to set. Garnish with the reserved green onions for a fresh pop and pass sturdy dippers like Fritos scoops or celery sticks for contrast.