With generous layers of dulce de leche, bananas and whipped cream, this dazzling pie is not for the faint of heart. The banoffee or banoffi pie, a mash-up of banana and toffee, was created in 1971 by the chef Ian Dowding and Nigel MacKenzie, the owner of the Hungry Monk, a now-closed restaurant in Sussex, England. The original recipe called for a traditional pie crust, homemade dulce de leche and coffee-flavored whipped cream, but we’ve simplified it for the home cook by using a graham…