Combine salmon and smoked salmon for the ultimate homemade fish fingers.
Place the salmon, smoked salmon and springonions into a bowl and gently mix together with a fork. Season with salt and freshly ground black pepper.
Mould the mixture into 10cm/4in x 2.5cm/1in fingers. Sprinkle the flour and polenta mixture on separate plates and beat the eggs in a bowl.
Dredge the salmon pieces in the flour, then dip into the egg and roll in the polenta and breadcrumb mixture. Set aside on a tray in the fridge until needed.
Pour the vegetable oil into a deep heavy-based frying pan until it is 3cm/1in in depth. Heat over a medium heat. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Fry the salmon piecess in the hot oil, turning regularly, for 5-6 minutes or until golden-brown and crisp. Remove from the pan with a slotted spoon and set aside to drain on kitchen paper.
For the sauce, place all of the ingredients into a bowl and mix until well combined.
To assemble the sandwich, spread some sauce on a slice of bread: place a handful of rocket and 3 fish fingers on top. Squeeze the lemon juice over, cover with another slice of bread and serve.
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