In a medium saucepan, combine sugar and cornstarch. Add half-and-half and egg yolks, whisking to combine. Bring to a boil over medium-high heat; cook for one minute, whisking constantly.
Remove from heat, and gradually whisk in butter. Stir in sour cream and vanilla. Let cool slightly; cover and refrigerate until chilled.
In resealable jars, layer custard mixture, bananas, and vanilla wafers; repeat layers as desired. Seal jars with lids, and refrigerate over night.
When ready to serve, top pudding with sweetened whipped cream.