Season the mahi-mahi fillets with salt on both sides.
Leave for 5 minutes.
Put the fish into a sous vide bag together with olive oil and cook for 20-30 minutes at 135°F.
Meanwhile, sautee black beans and onions in a pan.
Pour in white wine and squid ink.
Simmer until fully reduced.
Puree the black bean mixture in a food processor.
Serve fish on top of bean puree.
Garnish with basil oil.