In a large plastic bowl place the pork, with the garlic, onions, scallions, vegetable oil, salt and pepper.
Mix well, cover and refrigerate overnight or at least 3 hours.To make the Pipían: Cook the potatoes in a pot with water for 20 minutes or until tender.
Drain and gently mash the potatoes. Set aside.
Place the masarepa in a large bowl, add the water, salt, sazon Goya or color and aliños.
Place 1 piece of the leaf on a work surface and place a second leaf on top, pointing in the opposite direction, like forming a cross.
Spread about 5 tablespoons of masa in the center of the banana leaves, at the point where they connect and form a cross.
Place 1 piece of pork on top of the masa and place about 2 tablespoons of pipían on top of the meat.Fold the banana leaves up, one of the four sides at the time, so that the leaves enclose all of the filling, like you’re making a package. Tie with butcher’s string. Continue the process until all the tamales are wrapped and tied.Bring a large pot with salted water to a boil.
Add the tamales and then reduce the heat to low. Cover and cook for about 1 hour.
Remove the tamales from the pot and let them sit for about 5 minutes before serving.