Whisk together the dry ingredients in a saucepan. Combine the sugar, cornstarch, and salt, ensuring they are evenly mixed before adding the liquids.

Incorporate the milk and heavy cream slowly, whisking to avoid lumps.

Cook over medium heat, stirring until the mixture thickens, about 8-10 minutes.

Temper the egg yolks with the hot mixture and return to heat for 1-2 more minutes.

Remove from heat and stir in butter and vanilla until smooth.

Layer the pudding in a serving dish, starting with vanilla wafers, banana slices, and custard.

Chill for 4 hours before serving, covered with plastic wrap.