Cut tuna into chunks and pass through meat grinder with a medium die.
In a medium-sized bowl, combine with the breadcrumbs, egg, cheese, raisins, and pine nuts. Combine until the mixture forms a thick homogenous paste. Lightly salt and pepper. Using a tablespoon measurement, scoop heaping tablespoons of the tuna mixture and roll between your palms to form round-shaped croquettes.
Fill a deep pan no more than halfway with the olive oil. Heat the oil over medium-high heat until it reaches 350 degrees. The oil should stay at or around this temperature throughout the frying process. Roll each tuna croquette into the flour to coat, shaking off any excess. Using a slotted spoon, carefully lower the meatballs into the hot oil and cook until they are a light golden brown, about 2 minutes. Remove with the same slotted spoon and leave to drain on a serving platter lined with paper towels. Season croquettes with salt and pepper while hot. Repeat until all the tuna has been used.
In a medium saucepan, heat 3 tablespoons olive oil over medium heat. Add the garlic and cook until soft and lightly toasted, about 7 to 8 minutes. Add the tomatoes and season, to taste, with salt and pepper. Use a potato masher to soften and break down the tomatoes. Add a drizzle of extra-virgin olive oil and cook tomatoes for about 8 to 10 minutes. Sprinkle with the chopped parsley and garnish with fennel fronds and some more drizzles of extra-virgin olive oil. Spoon some sauce on a plate, place a croquette on top and serve hot.