Combine the cream and milk in a saucepan. Place it over medium heat until it starts to simmer and add the mashed bananas.
Meanwhile, whisk together the sugar, pinch of salt, yolks, and vanilla extract. When the milk mixture comes to a simmer, temper the yolks by slowly streaming and whisking the hot mixture into the yolks. Return the mixture back to the saucepan over medium heat. Stir constantly until it reaches 170F.
Remove the pan from the heat and you can either cool in an ice bath or in the refrigerator. Make sure to cover the mixture with plastic wrap.
Freeze your ice cream machine according to factory directions. Churn your ice cream base until it reaches the consistency of soft serve. Fold in the crushed Nilla crackers and freeze until firm.