For the yucca mofongo: Add the oil to a small stockpot to fill it about 4 inches up the side. Place the pot over medium-high heat and preheat to 350 degrees F (adjust the heat as needed throughout cooking to maintain that temperature).
Carefully add the yucca to the hot oil and fry until pale golden brown and tender when pierced with a knife, 8 to 10 minutes.
While the yucca is frying, mash the garlic in the bottom of a serving bowl. When the yucca are ready, carefully remove about one-third of them from the oil and transfer to the serving bowl. Add some of the pork rinds, sprinkle lightly with salt and mash them into a chunky paste. Continue adding the remaining yucca and pork rinds to the serving bowl in 2 more batches, mashing them into a chunky paste. Adjust the final seasoning with salt as needed. Keep warm until ready to serve.
For the fish stew: Place a large high-sided skillet over medium-high heat with the olive oil. Add the culantro, chile peppers, garlic, cilantro and onions to the skillet and cook, stirring frequently, until aromatic, 2 to 3 minutes. Add the tomato sauce and tomato paste and continue cooking until the vegetables are tender, 4 to 5 minutes more. Sprinkle the fish with the adobo seasoning and add it to the skillet. Simmer, gently stirring occasionally, until the fish is cooked through, 4 to 5 minutes. Adjust the seasoning with salt as needed.
Serve the fish stew with the mofongo.