Season and Sear Chicken: Begin by seasoning 500g of skinless, boneless chicken thighs with 1/2 tsp each of salt and pepper. Heat 2 tbsp of unsalted butter in a large pot over medium-high heat until foamy. Add the chicken to the pot, browning for 3 minutes on one side until lightly golden, then flip and cook for another 2 minutes. It's okay if the chicken isn't cooked through; it will continue cooking later. Remove the chicken and set it aside on a plate.
Sauté Vegetables for Flavor Base: Lower the heat to medium-low. Add finely chopped onion and sliced celery (or carrots if substituting) to the same pot, cooking for about 3 minutes until the onion softens.
Deglazing with Wine: Increase the heat to high and add 1/2 cup of dry white wine to the pot, scraping up any bits stuck to the bottom with a spatula. Allow the wine to simmer and reduce by half. If opting out of wine, you can substitute with additional chicken stock.
Broth and Pasta Addition: Pour in 4 cups of low sodium chicken stock and 3 cups of water. Season with 1 tsp cooking salt and 1/2 tsp black pepper, then bring to a boil. Add 250g of small pasta shells, cooking according to the packet's instructions, stirring occasionally to prevent sticking.
Return Chicken to Pot: While the pasta is cooking, chop the chicken into 1.5cm pieces and add it back into the pot to finish cooking through.
Completing the Soup: Once the pasta is tender, reduce the heat to low. Stir in 1 cup of finely grated parmesan cheese until melted. Incorporate a cornflour slurry (2 tsp cornflour mixed with 2 tsp water), followed by 1 cup of heavy cream and 2 cups of packed baby spinach. Continue stirring for about a minute until the spinach wilts and the soup thickens slightly.
Serving: Dish the soup into bowls and garnish with 1/2 cup of chopped sun-dried tomatoes and a drizzle of their oil. Serve hot, with extra lime wedges on the side for an added tang if desired.