In a medium saucepan, whisk together the sugar, flour, and salt.

Gradually whisk in the milk until the mixture is smooth.

Place the saucepan over medium heat and cook, stirring constantly until it thickens and bubbles, about 8-10 minutes.

In a separate bowl, beat the egg yolks, then slowly add a few spoonfuls of the hot pudding mixture to the yolks, whisking constantly.

Pour the tempered yolk mixture back into the saucepan and continue cooking for another 2 minutes, stirring constantly until thickened.

Remove from heat and stir in the vanilla extract.

In a baking dish, layer Nilla Wafers, banana slices, and the pudding. Repeat until all ingredients are used, finishing with pudding on top.

Cover and refrigerate for at least 4 hours or overnight.