Preheat oven to 350 degrees F.

Crush the graham crackers into fine crumbs using a food processor or rolling pin and ziploc bag. Add the melted butter and granulated sugar, mixing until the crumbs are evenly moistened.

Press the crust mixture into a 9-inch pie plate or springform pan using a flat-bottomed glass or measuring cup to help compact the crumbs on the bottom and up the sides. Bake for 10 minutes to set the crust, then remove from the oven and cool completely.

While the crust bakes, prepare the caramel toffee filling by melting the butter and brown sugar in a medium saucepan over medium heat. Add the sweetened condensed milk, then bring the mixture to a boil for 3-4 minutes, stirring vigorously, until it thickens and darkens in color a bit to a lovely toffee shade that is close to the color of peanut buttr. Pour the warm toffee filling into the prepared crust, then let it cool completely and chill for 1-2 hours until firm.

Beat the heavy cream, sugar, and vanilla on medium-high speed in a stand mixer fitted with the whisk attachment until medium peaks start to form, usually around 3-4 minutes. The whipped cream should be light, fluffy, and a good consistency for piping. Be careful not to overbeat to stiff peaks.