Rinse the fish under cold running water, then pat dry with paper towels. Season inside the cavity with salt and pepper.
Pour the milk into a bowl. Season the flour with salt and pepper on a plate. Dip each fish in the milk, then dust them in the flour, tapping off the excess.
Heat the oil in a large frying pan. Add half of the butter. Once it foams add the fish. Cook for 7–8 minutes on a fairly low heat until the underside is golden brown. Turn the fish over using a spatula then cook on the other side for a further 7–8 minutes.
Lift the fish onto a serving dish and cover with foil to keep warm. Discard the pan juices and wipe out the pan with paper towels. Melt the rest of the butter in the pan, season to taste, add the lemon juice, parsley and almonds. Spoon over the trout and serve.