Preheat the oven to 375° and have ready a greased, 4-cup capacity, oven-safe dish.
In a medium-sized saucepan over medium heat, melt the butter. Do not allow butter to burn. Add the green onions and sauté 1 minute. Add the garlic and sauté about 1 minute more.
Add the cream cheese and cream, and stir until combined and smooth. Stir in the lemon juice, Worcestershire, salt, and cayenne, followed by 1 cup of grated Cheddar cheese. Add the crab and stir once more.
Transfer to the serving dish and top with the remaining ½ cup of Cheddar and the Parmesan (if using). Bake for 16-18 minutes, until hot and bubbly. Garnish with green onion tops, serve, and enjoy.