Preheat the oven to 375°F (190°C). Lightly grease a 1-quart baking dish or small cast-iron skillet.
This size helps the dip heat evenly and brown on top.
Soften the cream cheese. If it’s cold, microwave it in 10–15 second bursts until it’s easy to stir. Soft cream cheese blends smoothly and prevents lumps.
Mix the base. In a medium bowl, combine cream cheese, sour cream, mayonnaise, Dijon, Old Bay, garlic powder, onion powder, smoked paprika, lemon juice, and zest. Stir until completely smooth.
Add cheeses and herbs. Fold in mozzarella, Parmesan, green onions, and parsley.
Taste and adjust seasoning with a pinch of salt and pepper if needed.
Fold in the crab. Gently add the lump crab, breaking up large pieces but keeping some chunks intact. Overmixing will shred the crab and make the dip dense.
Transfer and top. Spoon the mixture into the baking dish. Smooth the top and sprinkle with a little extra Parmesan and a pinch of Old Bay for color.
Bake. Bake for 18–22 minutes, until hot and bubbling at the edges.
For a browned top, broil for 1–2 minutes at the end, watching closely.
Rest and serve. Let it sit for 5 minutes to set. Sprinkle with extra green onions or parsley. Serve warm with your favorite dippers.