¼ tsp. freshly ground white pepper
Chopped fennel fronds, for garnish
In a medium saucepan, bring shrimp shells and broth to simmer over high heat. Reduce heat to low and simmer 30 minutes. Strain stock into bowl, discarding shells. Set aside.
In a large Dutch oven or flameproof casserole dish, heat butter over medium-low heat. Add fennel and shallots, cover and cook until fennel softens, about 10 minutes. Sprinkle with flour and stir 1 minute. Gradually stir in broth. Stir in vermouth and tomato paste. Bring to simmer over high heat, stirring to dissolve tomato paste. Return heat to medium-low and simmer, uncovered, until fennel is very tender, about 10 minutes. Add shrimp and cook until pink and firm, about 3 minutes.
Pour mixture into wire sieve set over bowl. Transfer solids with about 2 cups of liquid to blender and process until smooth. Return puree and cooking liquid in bowl to saucepan. Add cream and liqueur. Bring just to simmer over medium heat. Season with salt and pepper. Serve hot, garnishing each serving with chopped fennel fronds.
Nutrition information per serving: