I came up with this recipe after tasting and loving mofongo (the Puerto Rican dish made with green plantains and pork crackling). I originally planned to make a vegetarian version of mofongo; however, I continued to adapt it to make it easier (omitting the deep fat frying), moister (adding sautéed onions) and crispier (making them into cakes which I pan fried). My family loves these as the flavor and texture are amazing. They are easily adapted to vegan by omitting the butter in the onion mixture. I love them as is, but they are also wonderful as a base to a fried egg. —Leila
Peel and chop onion. Heat oil in a frying or sauté pan over low heat. Add chopped onions, kosher salt and sugar. Cook slowly, stirring occasionally until soft and translucent (do not brown) ~ 20-30 minutes. Add butter and continue cooking for 5 more minutes. Set aside. (This can be done earlier in the day or the day before and refrigerated).
Green plantains can be challenging to peel if they are extremely green; therefore, I prefer to purchase 1 or 2 days before using (see the picture for the preferable ripeness). Cut off the plantain ends and score the peel lengthwise and peel off. Slice thin (about 1/4" thick) slices on a diagonal. Pour oil into a frying pan to a depth of ~ 3/8". Heat oil over medium-high heat until shimmering. Pan fry plantains flipping over halfway through cooking time until cooked through and they can be pierced with a fork ( ~ 3-5 minutes total). They won't be fork tender but they will be able to be pierced. Don't overcook. It's fine to brown a little but you're not going for dark brown. Remove from pan and blot dry with paper towels.
While still hot, place in a food processor and pulse until only small chunks remain. Add 1/2 cup of sautéed onion mixture and kosher salt to taste. Pulse again so the onion mixture is well incorporated. The plantain mixture is starchy, and easy to form into cakes, but they will dry out if not pan frying right away, so cover well. Reheat the oil in the frying pan over medium-high heat. When the oil is hot, gently lay the plantain cakes in the hot oil and brown on both sides. They're best when a beautiful brown crust forms. Serve hot or at room temperature.