Chop the garlic and brown it in a pan in extra-virgin olive oil. Add the cod fillets and cook over low heat, covered, until golden brown.
2.
Meanwhile, roast the sweet potatoes in the oven for about 45 minutes at 356 ºF. Blend them in a food processor with olive oil, a splash of white wine vinegar, and salt and pepper until you get a thick paste. If it is too thick, you can add a splash of milk or vegetable milk to taste.
3.
To assemble the dish, start with a bed of sweet potato purée, place a cod fillet on top and garnish with a few olives.