Method

1| Preheat oven to 180°C. Line an oven tray with baking paper. Heat oil in a large heavy-based pan over a medium heat. Add garlic, cook for 30 seconds, then add breadcrumbs and cook, stirring, for 3-5 minutes until golden. Stir in almonds, transfer to a bowl and set aside.
2| Remove any skin and bones from the fish fillets. Cut perch into 1.5cm-thick slices lengthways. Cut salmon into 1cm-thick slices lengthways. Put in a bowl and pour over lemon juice, reserving the rind. Put peas in a heatproof bowl and cover with boiling water. Stand for 30 seconds, drain, then mash with a fork.
3| Brush a sheet of filo pastry with butter and sprinkle over a light, even covering of the breadcrumb mixture. Top with another sheet of filo and repeat process until all the mixture and filo are used. Spoon mashed peas across the length of the filo, 5cm in from the edge closest to you.
4| Put prepared fish on top of the peas. Sprinkle each with a little lemon rind. Season to taste with sea salt and pepper. Fold sides of filo over fish and roll up firmly. Brush with butter and put onto the prepared tray. Bake for 25-30 minutes until golden. Serve strudel immediately, cut into thick slices.