1. Have baked 9-inch pie shell ready.
2. In a large saucepan, scald the milk.
3. In another saucepan, combine the sugar, flour, and salt; gradually stir in the scalded milk.
4. Over medium heat, stirring constantly, cook for 2 minutes longer.
5. In a small bowl, slightly beat the 3 egg yolks. Stir in a small amount of the hot mixture into the beaten yolks; when thouroughly combined, stir yolks into hot mixture.
6. Cook for one minute longer, stirring constantly.
7. Remove from the heat and blend in the butter and vanilla.
8. Let sit untill lukewarm.
9. When ready to pour, slice bananas and scatter in pie shell; pour warm mixture over bananas.