Toss the sweet potato puree, oats, eggs, milk, vanilla, baking powder, and spices into your blender. Pulse until the mixture is completely smooth. Let the batter rest for 2-3 minutes while the iron heats; this allows the oats to hydrate for better structure.
Preheat your waffle iron until it is screaming hot. Give it a quick spritz of non-stick spray if your iron is prone to sticking.
Pour about 3 tablespoons of batter (for mini waffles) or 1/2 cup (for full-sized) onto the center of the iron. Close the lid and cook until the steam stops rising, usually about 4 minutes for mini waffles.
Carefully remove with a silicone spatula. Serve immediately or let cool completely on a wire rack before freezing for a 'homemade Eggo' experience.