Combine 3/4 cup of the sugar, the cornstarch and salt in a 3-quart saucier. Add the eggs and egg yolk and whisk to combine. Add the milk and whisk until well combined, about 30 seconds. Cook over medium-low heat, stirring constantly until the mixture reaches 172 to 180 degrees F, approximately 5 to 10 minutes. The mixture will begin to thicken and bubble around the edges. Remove from the heat and whisk in the butter, 1 piece at a time, being sure each piece is fully incorporated before adding the next. Whisk in the vanilla extract. Cover the surface of the pudding with a round piece of parchment and refrigerate until the pudding reaches 45 degrees F, approximately 2 hours.
Lay the vanilla wafers on a half sheet pan. Slowly and evenly pour the banana liqueur over the cookies. Set aside for 10 minutes.
Toss the banana slices with the lemon juice in a small bowl and set aside.
Spread a small amount of pudding in the bottom of a 1 1/2-quart glass mixing bowl. Cover with a layer of vanilla wafers, followed by a layer of banana slices. Spoon 1/3 of the remaining pudding on top of the bananas and repeat, ending with a layer of pudding.
Put the whipping cream in the bowl of a stand mixer, add the remaining 2 tablespoons of sugar and whisk just until stiff peaks form. Spoon the whipped cream over the cooled pudding and spread to cover completely. Top with any remaining soaked cookies. Refrigerate for 30 minutes before serving. Store, covered, in the refrigerator for up to 3 days.