Heat the olive oil in a large (12-inch) saute pan over medium heat. Add the fennel and saute for 5 minutes, until tender but not browned. Turn the heat to medium-low, add the garlic and red pepper flakes, and cook at a very low sizzle for 2 to 3 minutes, until the garlic just begins to color.
Pat the shrimp dry with paper towels, add them to the pan, and toss together with the fennel and olive oil. Spread the shrimp in one layer and cook over medium heat for 2 minutes on one side. Turn the shrimp and cook for 2 minutes on the other side, until they¿re pink and just cooked through.
Off the heat, sprinkle with the parsley, 1 tablespoon of chopped fennel fronds, the Pernod (if using), the fleur de sel, and black pepper and serve it with bread to soak up all the pan juices.