Fill a large bowl with ice water. In a small bowl, whisk the egg yolks and set aside. In a medium saucepan, combine the cream, milk, sugar, and salt, warming over medium heat until the mixture is hot and the sugar dissolves, about 4 minutes. Temper the eggs by slowly pouring ½ cup (118 ml) of the warmed cream mixture into the yolks, whisking constantly until well combined.
Return the warmed yolks to the pan with the remaining cream mixture. Heat the custard over medium-low heat, stirring constantly, until it thickens and coats the back of a spoon. Remove from heat and strain the custard through a fine-mesh sieve into a medium bowl.
Cut the bananas into chunks and purée them in a blender with the nutmeg and lemon juice until smooth. Add the hot milk mixture and blend to combine. Pour the custard into a medium bowl. Place the bowl in an ice water bath and cool for about 20 minutes, whisking occasionally. Add the vanilla and stir to combine. Cover and refrigerate until well chilled, at least 4 hours or overnight. Freeze the vanilla wafers overnight.
Once chilled, pour the ice cream base into an ice cream maker and churn according to the manufacturer’s instructions. When churning is complete, gently fold in the vanilla wafers. Transfer the mixture to a freezer-safe container and freeze until firm, at least 4 hours.