Whisk the eggs in a large bowl and set aside.

In a pot over medium heat, add flour, sugar, salt, milk, and vanilla extract. Whisk continuously until the mixture comes to a boil.

Reduce heat to medium-low and continue whisking until slightly thickened.

Slowly add a few tablespoons of the hot pudding mixture into the eggs while whisking constantly to temper the eggs.

Pour the combined mixture back into the pot and cook over medium heat until it reaches a gentle boil, whisking continuously.

Remove from heat and stir in mashed banana and sweetened condensed milk.

Transfer pudding to a container and let cool at room temperature for 30 minutes, then refrigerate for 3–4 hours until fully chilled.

Whip heavy cream and sugar on high speed until thick and fluffy. Refrigerate until ready to use.

Layer mason jar banana pudding by adding pudding, banana slices, Nilla wafers, and whipped cream into jars. Repeat layers.

Top with a banana slice and wafer. Let sit 30 minutes before serving.