Heat olive oil in a large pan and fry onion and garlic for 5 minutes.
Add fresh tomatoes, canned tomatoes, and tomato paste then bring to a boil.
Simmer the sauce for 15 minutes.
Stir in basil leaves halfway through the simmering time.
Season with salt and pepper, cool slightly, and blend until smooth.
Boil potato chunks in salted water until tender.
Drain potatoes and heat briefly to remove excess moisture.
Pass potatoes through a ricer or sieve into a bowl.
Mix in flour, parmesan, seasoning, and 15ml of olive oil until smooth.
Transfer dough to a piping bag fitted with a large nozzle.
Pipe and cut 2.5cm lengths of dough directly into boiling water.
Poach gnocchi for 2 minutes once they float to the surface.
Drain gnocchi on kitchen paper using a slotted spoon.
Fry gnocchi in olive oil until golden-brown and keep warm.
Season the lemon sole fillets with salt and pepper.
Fry fish in olive oil for 3 minutes until golden.
Flip the fish and cook for one further minute.
Coat gnocchi with the tomato sauce and heat through.
Plate gnocchi and top with half a fillet of lemon sole.