Inside-Out Apple Pie à la Mode

Preheat the oven to 375°F.
To make the crust, stir together the oats, pecans, muscovado sugar, salt, and cinnamon in a large bowl. Add the melted butter and stir to combine. Press the mixture into the bottom and up the sides of a 9-inch pie pan and bake until toasted, 10 to 12 minutes. Remove from the oven and use the back of a spoon to push the crust back up the sides, as it will have fallen a bit, and set on a wire rack to cool completely.
Remove the ice cream from the freezer and allow it to soften for about 10 minutes. Scoop the ice cream into the pie shell and spread it in an even layer. I find this works best by using a large spoon and dipping it in warm water every so often to help spread the ice cream out flat. Put the pie back in the freezer to firm up for at least 1 hour, or up to 3 days, placing a piece of plastic wrap on top if you'll be freezing it for more than a few hours.
To make the topping, melt the butter in a large sauté pan. Add the apple slices and sauté until tender, 8 to 10 minutes. Add the muscovado sugar, cinnamon, and vanilla and continue cooking until a sauce forms, another 2 minutes.
Remove the ice cream pie from the freezer, cut into six pieces, wiping off your knife between each slice, and spoon the warm apples on top of each slice. Alternatively, let the apples cool to room temperature and then pile them onto the ice cream pie before cutting into serving pieces. Garnish with the pecans or granola and serve immediately.