Peel and devein the prawns, reserving all the shells and heads for the stock. Refrigerate the prawn meat for later use.

Melt the butter in a large pot over medium-high heat. Add the prawn shells and heads, cooking for 5-6 minutes until they turn bright pink and fragrant.

Add the chopped fennel bulb, onion, and garlic to the pot. Sauté for another 5 minutes until the vegetables begin to soften and lightly brown.

Stir in the tomato paste and paprika, cooking for 1 minute to deepen the flavor and coat the shells.

Pour in the white wine to deglaze the pot, scraping up any browned bits from the bottom with a wooden spoon. Let it bubble for 2 minutes.

Add the fish stock (or vegetable broth) and bring the mixture to a boil. Reduce heat to low, cover, and simmer gently for 25 minutes to extract all the flavors.

Strain the soup through a fine-mesh sieve into a clean saucepan. Press down hard on the shells and vegetables with the back of a ladle to extract as much liquid and flavor as possible, then discard the solids.

Return the strained broth to medium heat and bring to a gentle simmer. Stir in the heavy cream and season with salt and black pepper to taste.

While the soup simmers, heat the olive oil in a separate skillet over medium-high heat. Season the reserved prawn meat with salt and pepper, then sear for 2-3 minutes per side until opaque and cooked through.

To serve, ladle the hot bisque into bowls and top with the seared prawns. Garnish with the reserved fennel fronds and a crack of black pepper.