In a large pot, heat the EVOO over medium. Add the chorizo and cook, breaking it up with a spoon, 6 minutes. Transfer to a plate.
Add the onion, carrot and garlic to the pot. Cook, stirring occasionally, until vegetables soften, about 8 minutes. Add the potatoes, tomatoes and stock; boil. Reduce heat and simmer until potatoes are tender, about 20 minutes. Stir in the chorizo.
Nestle fillets in the soup and simmer until fillets are opaque and flaky, 5 to 7 minutes. Divide chowder among bowls; top with parsley.