Combine the ½ cup melted butter and 2 ½ cups graham cracker crumbs and press into the bottom and up the sides of a 9" pie plate. Set aside.
Filling
Lightly grease a medium microwave-safe bowl and add 1 ½ cups mini marshmallows. Microwave on high in 20-second intervals just until puffed and soft -- stir until completely melted and smooth.
In a medium bowl, whisk together 2 (3.9-ounces) packages instant chocolate pudding mix and 3 cups 1% milk until smooth. Add marshmallows and whisk vigorously until smooth.
Pour into the prepared crust and refrigerate until set, at least 2 hours.
Marshmallow Cream
Place 3 egg whites, ¾ cup granulated sugar, and ¼ teaspoon cream of tartar in a glass bowl and whisk to combine. Add 1/2-1-inch of water to the bottom of a small pot (make sure that the glass bowl will rest on top and not touch the water) and bring to a simmer over medium-high heat.
Reduce heat to medium and place glass bowl over top, whisking constantly until egg whites are warmed and the sugar is dissolved.
Remove from heat and whisk with an electric mixer on high until stiff peaks form, about 5-8 minutes.
Spread the marshmallow cream over the top of the pie and toast with a kitchen torch if desired. Chill for at least 2 hours before serving.