Prepare the lobster by thoroughly halving the pre-cooked lobster tails lengthwise, removing the meat, chopping into bite-sized pieces, and returning to the shell halves.

In a medium skillet, melt 2 tablespoons of butter over medium heat. Add finely chopped shallots and sauté for about 3-4 minutes until soft and translucent.

Pour in ½ cup of white wine and 1 cup of fresh fish stock, bringing the mixture to a gentle boil. Reduce by half, then stir in 1 cup of heavy cream and thicken over low heat for about 5 minutes. Add fresh lemon juice, hot English mustard, and season with salt and black pepper.

Carefully pour the creamy sauce over lobster meat in the shells, sprinkle with Parmesan cheese, and broil for 3-4 minutes until the cheese is golden and bubbly.

Remove from oven, let rest for a minute, and garnish with freshly chopped parsley before serving.