Creating the Lobster Pot Pie involves several straightforward steps:

1. Preheat the Oven: Start by preheating your oven to 425°F (220°C).

2. Sauté the Aromatics: In a large skillet over medium heat, melt the butter. Add the chopped onions and garlic, cooking until softened—about 3-4 minutes.

3. Make the Roux: Sprinkle in the flour, stirring constantly for about 1-2 minutes, until the mixture becomes a light golden color.

4. Add Liquids: Gradually whisk in the chicken or seafood stock and heavy cream. Continue to stir until the mixture thickens, about 5 minutes.

5. Incorporate Vegetables and Seafood: Add in the cooked lobster, frozen peas and carrots, and cooked potatoes to the sauce. Stir well to combine. Season with thyme, salt, and pepper to taste. Remove from heat.

6. Prepare the Pie Crust: Roll out the refrigerated pie crust and place it into a 9-inch pie dish, trimming any excess overhang.

7. Fill the Pie: Pour the lobster mixture into the prepared crust, spreading it evenly.

8. Top with Crust: Place another pie crust over the filling. Cut slits in the top to allow steam to escape, and crimp edges to seal.

9. Apply Egg Wash: Brush the crust with the beaten egg to achieve a golden finish while baking.

10. Bake: Place the pie in the preheated oven and bake for 40-45 minutes, or until the crust turns a beautiful golden brown.

11. Cool: Once done, remove the pie from the oven and let it cool for 10-15 minutes before serving.

These steps will ensure that your Lobster Pot Pie comes out perfectly delicious and visually enticing.