Preheat the oven to 200°C.
Bring the fish stock to a gentle simmer in a pan.
Melt half of the butter in a heavy pan and soften the shallot, garlic, and leek.
Add the rice and stir for one minute to coat with butter.
Pour in the wine, boil, and reduce the liquid by half.
Slowly add the warm stock one ladle at a time, stirring until absorbed and rice is al dente.
Stir in the flaked cooked haddock.
Mix in the remaining butter, mascarpone, parmesan, and parsley, then season.
Pan-fry haddock fillets in butter for one minute per side, then roast in the oven for 6 to 8 minutes.
Blend parsley and olive oil in a food processor and strain through a sieve.
Serve the risotto topped with a haddock fillet and a drizzle of parsley oil.