Preheat the oven: Preheat your oven to 350°F Crush the graham crackers: If using whole crackers, crush them in a food processor or place them in a Ziploc bag and crush them until you have fine crumbs.

Mix the dry ingredients: In a medium-sized mixing bowl, stir together the graham cracker crumbs and sugar.

Add melted butter: Pour in the melted butter and mix until combined. The mixture will be crumbly.

Press the crust: Press the crumb mixture into the bottom of a 9 x 13-inch casserole or baking dish. See notes below for tips on how to press the crust.

Bake the crust: Bake for 10 minutes.

Cool: Remove from the oven and set aside to cool completely. Turn off the oven, as the crust is the only part of this dessert that needs to be baked.

Prepare the filling: While the crust is cooling, start preparing the filling.

Heat the mixture: Pour the milk and pineapple juice mixture into a saucepan. Add the marshmallows. Note: The marshmallows will expand slightly when heated, so choose a saucepan that is large enough.

Melt the marshmallows: Heat the liquid and marshmallows over low heat, stirring constantly to prevent burning, until the marshmallows are completely melted and dissolved. You can also heat the mixture over a double boiler if you prefer.

Cool the mixture: Remove the saucepan from the heat and allow the mixture to cool completely.

Make the whipped cream: While the filling is cooling, whip the heavy whipping cream and vanilla extract in a stand mixer or with a hand mixer until soft peaks form.