2 cups pureed very ripe bananas (4 to 5 medium bananas), 1 cup heavy cream, 3 tablespoons sugar, 3/4 teaspoon pure vanilla extract, 1/8 teaspoon salt. In a medium bowl, stir the banana puree with the cream, sugar, vanilla, and salt. Let stand briefly, then stir again to make sure that the sugar is dissolved. Chill. For an extra-cold start, put the mixture in the freezer for 20 minutes, stirring once or twice to prevent freezing. Freeze the mixture according to the instructions for your ice cream machine. Serve soft, or transfer to an airtight container and freeze, until the ice cream is hard enough to scoop, at least 3 to 4 hours. If the ice cream gets to hard, before serving let stand for a few minutes, put it in the refrigerator for 15 minutes or longer, or microwave it on low (defrost) for a few seconds until scoopable.