In a heavy frying pan over medium-high heat, toast the chickpea flour, stirring constantly or shaking the pan, just until it begins to smell toasty and darken slightly. Transfer immediately to a bowl.

Finely chop the peanuts and add to the bowl with the chickpea flour.

One at a time, heat the coriander seeds, caraway seeds, dill seeds and sesame seeds in a small skillet over medium-high heat, shaking the pan or stirring constantly, just until each is fragrant and beginning to smell toasty. Remove from the pan and allow to cool completely.

Working in batches, combine the coriander seeds, caraway seeds and dill seeds in a spice mill and grind to a powder. Transfer to the bowl with the chickpea flour and stir in the sesame seeds, salt, cayenne and sumac.

Heat a heavy cast-iron or nonstick frying pan over medium-high heat. Season the fish fillets if desired.

Place the dukkah on a baking sheet and lightly dredge the fish fillets in it. When the pan is very hot, add 1 tablespoon of the canola or grapeseed oil, and when it is rippling, just below smoking, add as many fish fillets as can comfortably fit into the pan without crowding it too much.

Cook for 1 ½ to 2 minutes, until browned, then turn over and cook another 1 ½ to 2 minutes (depending on the size of the fish), or until the fish is nicely browned on both sides. Remove to a warm platter.

Repeat with the next batch of fish, until all of it has been cooked. Douse with the lemon juice, sprinkle on the parsley and serve.