In a medium bowl, whisk together sugar, flour, and salt. Whisk in ½ cup milk and egg yolks.
In a large saucepan, bring remaining 3 cups milk to a simmer over medium heat, stirring frequently. Whisk 1 cup hot milk into egg mixture. Whisk egg mixture into remaining hot milk in saucepan. Bring to a boil over medium heat, stirring constantly. Cook, stirring constantly, until thickened, about 3 minutes. Remove from heat. Add butter and vanilla, stirring until butter is melted. Let cool for 10 minutes, stirring occasionally.
In a 13×9-inch baking dish, arrange wafers in a single layer. Top with banana slices; spread pudding over bananas. Spread whipped cream over pudding. Cover and refrigerate for at least 2 hours or up to 6 hours. Garnish with vanilla wafers and pecans, if desired.
Notes
Kitchen Tip: Strain the finished pudding through a fine-mesh sieve for an extra-smooth filling.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/banana-pudding/