Preheat oven to 375°F (190°C). Lightly butter a shallow baking dish.
In a mixing bowl, beat softened cream cheese until smooth.
Stir in mayonnaise and sour cream until fully combined and silky.
Add Dijon, lemon juice, Worcestershire sauce, shallot, and seasonings; mix well.
Fold in 3/4 cup shredded cheddar, Parmesan, and chopped chives.
Gently fold in lump crab meat, taking care not to break the lumps.
Taste and adjust salt, pepper, lemon or spice as needed.
Transfer mixture to prepared baking dish and smooth the top.
Sprinkle remaining cheddar over the surface and dot with melted butter if using.
Bake 15–20 minutes until bubbly and lightly golden on top.
Broil 1–2 minutes if you want a deeper golden crust—watch closely, then remove and let rest 3–5 minutes before serving.