My Mom cooked from scratch long before it became trendy to do so. I always liked when she made homemade pudding and there is a definite flavor difference you just can't get from any boxed pudding mix. With a little variation, this traditional vanilla pudding base can become just about any flavor you desire.
In a large heavy saucepan, bring milk and cream to a simmer. In a bowl, whisk together egg yolks, sugar, cornstarch and salt. Whisk a small amount of hot milk mixture into egg yolk mixture; return all to pan, whisking constantly.
Bring to a gentle boil; cook and stir 2 minutes. Remove from heat. Stir in butter and vanilla. Cool 15 minutes, stirring occasionally.
Line bottom of a 3-qt. trifle, or other glass bowl, with half the peanut butter cookies; cover with half the banana slices followed by half the pudding. Repeat layers. Press plastic wrap onto surface of pudding to keep it from forming a film; refrigerate until cold - at least 2 hours. Just before serving, remove plastic and top with fresh whipped cream or whipped topping.