In a large pot, cover the cubed potatoes with cold water and season with salt. Bring to a boil, then simmer for 20 minutes or until tender. Drain. Using a potato masher, purée the potatoes with the oil. Let cool slightly, then add the egg, stirring quickly to ensure the egg does not cook. Cover and let cool.
Meanwhile, in a non-stick skillet over high heat, soften the onion in the oil. Add the sausage meat and cook, breaking it up with a wooden spoon as it browns. Add the water, tomato paste and paprika. Simmer until almost dry, about 5 minutes. Season with salt and pepper. Let cool.
Preheat the oil in a deep dryer to 350°F (180°C). Line a baking sheet with paper towels.
With your hands, shape the potato mixture into patties 1/2 inch (1 cm) thick using about 1/4 cup (60 ml) of the mixture for each patty. Place 1 tbsp (15 ml) of the filling in the centre, then pinch to seal the potato mixture around the meat. Shape into balls and set aside on a large plate.
In a shallow dish, lightly beat the eggs. Place the bread crumbs in another dish. Dip the potato balls into the egg and shake gently to remove any excess. Dredge in the bread crumbs. Dip a second time in the egg and the bread crumbs.
Working in batches, fry several bombas at a time for 2 minutes or until golden brown. Watch out for splattering. Drain on the paper towels.
Serve immediately with pimentón sauce and garlic mayonnaise.