Heat a sauté pan with butter and oil over medium heat.
Finely chop the shallots, and sauté them until translucent, without browning.
Add parsley, thyme, and white wine. Let it reduce a bit before adding the cream.
Grate lemon zest into the sauce and bring everything to a boil.
Place the two pieces of cod on separate pieces of parchment paper. Add them to the sauce. Reduce the heat so the sauce doesn't boil but merely simmers.
Steam the cod for about 10 minutes, checking regularly to ensure it doesn't overcook. Use a meat needle to check if the fish is done (insert the needle into the side of the fish, pull it out, and place the needle on your lip. If it feels warm, the fish is done).
Remove the fish and let it drain on a kitchen towel.
Let the sauce reduce a bit more and season with salt, pepper, and perhaps more lemon zest.