Place the plantains, water, and 1 teaspoon of salt in a large pot or Dutch oven. Bring to a boil, then reduce heat to medium-low and simmer until the plantains are fork-tender, about 10 minutes.
Skim off any foam and drain the water.
Transfer the plantains to a large bowl. Mash with a potato masher or fork. Stir in ¼ teaspoon of salt, vegan butter, and vegan milk until smooth. Set aside.
Lentil Filling
Heat olive oil in a saucepan or Dutch oven over medium heat. Add sofrito and cook, stirring constantly, until fragrant, 1 to 2 minutes.
Stir in walnuts, oregano, adobo seasoning, sazon, black pepper, and olives. Cook for 1 minute.
Add lentils and water. Stir well, then bring to a boil. Reduce heat to low and simmer uncovered for 20 minutes, or until lentils are tender.
Stir in tomato sauce and simmer for 5 more minutes. Remove from heat and set aside.
Assemble Pastelón
Preheat the oven to 350°F. Lightly grease an 8x8-inch baking dish.
Spread half of the mashed plantains evenly in the dish, pressing down to form a flat layer.
Add all of the lentil filling, spreading it evenly over the plantains. Top with the remaining mashed plantains, smoothing the surface. Brush the top with oil.
Cover with foil and bake for 25–30 minutes. Remove the foil and broil for 4–5 minutes until golden.
Let cool for 15 minutes before serving.
Notes
Feel free to top off the pastelón with vegan cheese. The vegan cheese can also be added between the layers, similar to lasagna.
I suggest using homemadesofrito. Store-bought sofrito just isn't the same.
This recipe serves about 6 people.
Be sure the plantains are very ripe. They need to be tender to the touch, so we can yield soft and creamy mashed plantains.