Heat the olive oil in a large pot over medium heat. Add the onion and cook for 4 to 5 minutes until it softens.
Stir in the garlic and thyme and cook for 1 minute until fragrant.
Pour in the white wine and let it simmer for 2 minutes to reduce slightly.
Add the diced tomatoes, fish broth, olives, bay leaf, salt, and pepper. Bring the mixture to a gentle simmer.
Place the cod pieces into the pot and cook for 5 to 7 minutes without stirring too much until the fish flakes easily.
Remove the bay leaf and sprinkle the parsley over the stew before serving.