Preheat oven to 350 degrees and adjust rack to middle position. Melt the butter in a large pot over medium heat. Add the onion, celery, and carrots and cook for 12 minutes, stirring occasionally until softened. Add flour and cook stirring with a wooden spoon for 2 minutes. Pour in the chicken stock, stir, and bring to a boil. Lower the heat and simmer. Tie the parsley, thyme and bay leaf together with kitchen twine and add to broth mixture. Simmer for 15 minutes. Remove broth from heat and stir in cream and sea salt. Pour soup into a blender and blend until smooth.

Pour soup into a large mixing bowl. Add potatoes, butter, sea salt, pepper, sour cream and 1 cup of cheese to soup and stir until combined. Pour mixture into a 9×13″ baking dish and top with remaining 1 cup cheese. Bake for 40 minutes until bubbling and golden brown. Cool for 15 minutes before serving. Ensure you arrive at the party on time!