1: Whack the oven on at 180C.

2: Put the potatoes onto a baking tray and cook in the hot oven for 1 hour. 

3: When the hour is nearly up, lay a sheet of foil over a flat surface. Lay the frozen fish fillets on top and drizzle with vegetable oil and a sprinkle of salt and pepper. Lay another sheet of foil the same size on top of the fish and scrunch up the edges to make a sealed parcel.

4: After the potatoes have been cooking for 1 hour, add the foil fish parcel to the tray in the oven and cook this all for another 30 minutes. 

5: Remove the tray with the potatoes and fish parcels from the oven - but leave the oven on. Take the cooked fish fillets out of the foil and pop them in a bowl. Using a sharp knife, cut the potatoes in half and carefully spoon out the hot and fluffy insides from the skins, and add this to the bowl – make sure to keep the potato skins intact!

6: To the same bowl, add the mayonnaise, mustard, a pinch of cayenne (or other) pepper, and frozen peas. Give it all a good mix. Spoon the fish and potato mix into each of the potato skins (you will have 4) and grate the cheddar over each one. 

7: Put the filled jackets onto the baking tray and pop them back in the oven for 20 minutes until warmed through and the cheese has melted. Serve up and dig in!