Place the yuca, water and salt in a medium pot. Cover with water and bring to a boil and cook about 30 minutes or until tender. Drain and set aside.
While the yuca is cooking, heat the oil and butter in a frying pan over medium heat. Add the scallions and tomatoes, stir and cook about 7 minutes. Add cumin, salt and pepper. Stir and cook 2 minutes more.
Add cream and cheese. Mix well and turn down the heat and cook for 3 minutes or until cheese has melted.
Place the yuca in a serving dish, add the chorizo slices and pour the sauce on top. Serve it warm and garnish with scallions.