Bring a pot of water to the boil before adding salt and the cauliflower florets. Cook for approximately 6 minutes or until the cauliflower is tender when pierced with a fork.
Using a slotted spoon remove the florets from the water and transfer them to a food processor along with the butter, cream and thyme. Blitz on high until a smooth puree forms. Season to taste. Transfer to a bowl and keep warm.
With the water still boiling, add the peas and blanch them for 3 minutes before draining and refreshing in ice water.
Place a frying pan over a medium high heat and add the butter and oil. When the butter is melted, season the fish with black pepper before placing skin side down to cook for 3-4 minutes.
Carefully turn the fish and add the spinach and peas, cooking until the leaves are wilted and the fish is cooked all the way through. Add another knob of butter at this point to the baste the fish as it cooks.
Spread the cauliflower mash across two warm serving plates. Top with peas, spinach and the cooked fish. Season with sea salt and black pepper and serve.
Any white fleshed fish works well here and even mackerel fillets would be a nice. The cauliflower mash is incredibly easy to make and is a great side dish to recreate for other recipes.