Heat the oven: Preheat to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
Prep the broccoli: If using fresh, steam or blanch the florets 2–3 minutes until bright green and crisp-tender. Drain well and pat dry.
If using frozen, thaw, drain, and squeeze out excess moisture.
Cook the bacon: Crisp the bacon in a skillet. Drain on paper towels and crumble. Reserve 1–2 teaspoons of the bacon drippings if you want extra flavor in the sauce.
Make the sauce: In a large bowl, beat the softened cream cheese until smooth.
Mix in sour cream (and mayo if using), ranch seasoning, garlic powder, onion powder, and black pepper. Stir in a splash of broth or milk until the sauce is creamy and spreadable.
Fold in the good stuff: Add the chicken, broccoli, half the bacon, and 1 1/2 cups of the shredded cheese. Stir until everything is coated and evenly distributed.
Assemble: Spoon the mixture into the baking dish and spread in an even layer.
Top with the remaining 1/2 cup cheese and the rest of the bacon.
Bake: Bake uncovered for 20–25 minutes, until bubbly around the edges and the cheese is melted and lightly golden.
Finish and serve: Let it rest 5 minutes to set. Sprinkle with sliced green onions or chives. Serve as-is, or with rice, cauliflower rice, or buttered noodles.