Season the fish and steam in a steamer for 4–5 minutes or until the fish has turned opaque.
Heat a frying pan over a high heat and add the olive oil. Fry the pancetta or bacon until crispy, then remove from the pan and set aside.
Place the peas, baby gem, thyme and wine in the frying pan and bring the pan up to a low simmer until the baby gem has softened slighty. Stir in the butter and season with salt and pepper.
Divide the pea mixture between 4 shallow bowls and top with the steamed grey mullet and a sprinkle of crispy pancetta or bacon.