1. Pre-heat the oven to 180°C, gas mark 4.

2. Heat the oil and add the onions, and cook for 10 minutes to soften, let them take a little colour.

3. Boil the potatoes and mash with a masher, no need to add oil, butter or milk and keep warm.

4. Add the olives, cooked onions, zest of lemon, parsley and season well.

5. Place 2 fillets onto a nonstick baking tray, straight from the freezer.

6. Top generously with the mash olive mix, then place a second frozen fillet on top and press down. Repeat with the second box of fish.

7. Place into the hot oven and cook for 20-25 minutes or until the fish is warmed through and hot.

8. Serve the fillets cut into 2 pieces or 4 single fillets, topped and baked, it’s up to you.

9. I like to serve this with a spoonful of mayonnaise and a tomato salad.