In a saucepot, cook the cream, half and half, and sugar on medium heat until warm, do not let it come to a boil.
While the base is heating, beat the egg yolks with the vanilla. Once the base is warmed, pour 1/4 cup of the base into the beaten eggs, stir until well combined, and then pour the egg mixture into the pot. Add the sliced bananas to the pot, as well.
Heat this on medium low for 5 minutes or until it gets slightly thick. Do not let it come to a boil. You’ll know it’s ready when it coats the back of your spoon.
Stir in the salt, nutmeg, and lemon juice, turn off the heat, cover the pot, and let it rest for 45 minutes.
Strain the custard, reserving the banana slices either for serving along with the frozen ice cream or for another use. Chill the custard overnight or for at least 4 hours, and then freeze according to your ice-cream maker’s instructions. When the ice cream is finished being churned, stir in the crushed vanilla wafer cookies.
Serve cold with reserved banana slices, if you like.