Cover plantains with water in 4-quart saucepot; bring to a boil over medium-high heat. Reduce heat and simmer 10 minutes or until plantains are tender. Drain and mash; set aside.
Meanwhile, cook bacon in 10-inch nonstick skillet over medium heat until crisp. Remove and drain on paper towels. Reserve 1 tablespoon drippings.
Heat reserved drippings in same skillet and cook onion, stirring occasionally, 4 minutes or until tender. Stir in garlic and cook 1 minute. Combine plantains, onion mixture, mayonnaise and 1/2 of the bacon in serving bowl. Garnish with remaining bacon.