Cook jumbo pasta shells until al dente according to package directions, then drain, rinse with cold water, and set aside.

Preheat your oven to 375°F (190°C) and lightly grease a 9x13 inch baking dish.

Melt butter in a skillet over medium heat, add shrimp and cook for 2-3 minutes until pink.

Add minced garlic and cook for 1 minute until fragrant, then remove shrimp from heat to cool slightly.

In a large bowl, combine softened cream cheese, heavy cream, Parmesan, lemon juice, lemon zest, salt, white pepper, and dill; stir until smooth.

Gently fold the wilted spinach and cooled shrimp into the cream cheese mixture, adding a pinch of cayenne pepper if desired.

Whisk together the condensed cream of mushroom soup and milk in a separate bowl, then spread half of this sauce evenly in the prepared baking dish.

Stuff each cooked jumbo pasta shell with the shrimp and spinach cream filling, then arrange them in a single layer over the sauce base in the baking dish.

Pour the remaining soup mixture evenly over the stuffed shells, ensuring they are mostly covered, and then sprinkle generously with shredded Italian blend cheese.

Bake for 20-25 minutes, or until the sauce is bubbly and the cheese is melted and lightly golden.

Let the dish stand for 5 minutes before serving to allow flavors to meld and sauce to set, garnishing with extra fresh dill if desired.