Meanwhile, in a small frying pan over medium heat, combine the coriander seeds, peppercorns, and anise seeds and toast, tossing or stirring frequently, until lightly toasted and fragrant, about 2 minutes. Immediately transfer the contents of the pan to a dish and stir in the fennel pollen. Let cool, then transfer to a spice grinder and process until finely ground. Stir the ground spices into the sauce and cook for 5 minutes more. Remove from the heat and let cool.