Blend sourdough bread into crumbs in a food processor, add lemon zest, pulse, and transfer to a bowl.
Season flour with salt and pepper on a plate and beat eggs in a separate bowl.
Bread the cod cheeks by coating in flour, then egg, then sourdough crumbs, and chill in the fridge.
Process peas, mint, chillies, lime juice, and crème fraîche into a rough paste and chill.
Heat oil in a deep fryer or saucepan to 190°C.
Fry cod cheeks in batches for 2 to 3 minutes until golden and drain on kitchen paper.
Serve the cod cheeks on a platter with lemon wedges and the pea salsa.