Begin by making your ice cream rounds to later fill your sandwiches.
Scoop about ¾ cup of ice cream into a mound on a plastic wrap lined baking sheet. Smooth the top with your fingers or with some more plastic wrap into an even round disk. Repeat so that you have four equal disks of ice cream.
Place the baking sheet into the freezer and freeze until solid.
Next, make the cookies. Preheat the oven to 350 degrees F.
Whisk together the melted butter and sugar until homogenous. Add the egg and vanilla.
In another bowl, combine the flour, cinnamon, baking soda, salt, oats, and nuts. Stir to combine before slowly adding the dry ingredients to the wet ingredients. This should be a thick batter.
Scoop your cookies into mounds slightly smaller than the ice cream disks. The cookies will expand in the oven. You should have 8 even cookies.
Bake for 12 minutes until the cookies are set, then remove from the oven.
Remove the cookies to a wire rack and allow them to cool fully.
Once the cookies are cooled, flip half of them over to their smooth side. Add a disk of ice cream to each inverted cookie. Place the other cookie on top of the ice cream and press lightly to adhere.
Return them to the freezer for at least an hour before serving. Enjoy frozen.