Creating your own Jumbo Lump Crab Au Gratin is simple if you follow these steps:

1. Preheat Oven: Begin by preheating your oven to 375°F (190°C).
2. Prepare Crab: Carefully check the crab meat for any shells and set it aside.
3. Make the Roux: In a medium pan, melt the butter over medium heat. Add flour and whisk continuously for about 1 minute until golden.
4. Add Milk and Cream: Gradually whisk in the milk and heavy cream, stirring until the mixture is smooth and thickened, about 3-4 minutes.
5. Season the Mixture: Stir in the Dijon mustard, Worcestershire sauce, Old Bay seasoning, garlic powder, onion powder, salt, and pepper. Mix well to incorporate.
6. Add Cheese: Remove the saucepan from heat and fold in ¾ cup of the shredded cheese until melted and smooth.
7. Combine with Crab: Gently fold the jumbo lump crab meat into the cheese mixture, being careful not to break up the crab.
8. Transfer to Baking Dish: Pour the mixture into a greased baking dish.
9. Prepare Topping: In a small bowl, combine the breadcrumbs with the remaining cheese. Sprinkle this mixture evenly over the crab mixture.
10. Bake: Place in the oven and bake for 25-30 minutes until the top is golden and bubbly.
11. Garnish and Serve: Remove from the oven, garnish with chopped parsley if desired, and serve hot.

Each step is straightforward and designed to guide you to a delectable end result. You’ll not only be pleased with the taste but also proud of your culinary skills!