Season the cod. Heat the olive oil in a frying pan and cook the cod over a medium heat to get a good colour on it, on both sides. You are not cooking it through, just colouring it (it’s good if the skin goes slightly crispy, though).
Carefully move the fish onto a baking sheet, flesh side up, and put into an oven preheated to 200 C. Roast for 12 minutes.
Get on with everything else while the cod is cooking. Add the bacon to the pan in which you cooked the fish and cook it over a medium – high heat until it is golden all over.
Lift out the bacon and set it aside. Add the onions and saute until soft and pale gold, then add the peas and stock. Bring to the boil, then turn the heat down to a simmer and cook for about 4 minutes, until the peas are tender and the stock has pretty much evaporated (there should just be a little juice around the peas).
Add the bacon back to the pan and heat it through. If you want to make it a little luxurious you can add the cream, but it’s optional.
Spoon the peas and bacon onto two plates and put the fillets of cod on top. Serve immediately.