Mix cookie crumbs and butter, press into 9" pie plate and refrigerate.
Put 1/2 and 1/2 , egg yolks, sugar and cornstarch, whisk until smooth and cornstarch is dissolved.
Cook whisking constantly until thickend; about 15 minutes. When thick, remove from heat and add butter and vanilla. Place 1/2 the sliced bananas in crust, top with 1/2 the pudding, repeat layers and refrigerate. About 4 hours or until set. Top with cool whip just before serving and garnish with oreo crumbs.