Preheat the waffle maker. Set a mini waffle maker (like a Dash) to medium-high heat. If you have a standard waffle iron, this recipe makes one larger chaffle; cook time may vary.
Mix the dry ingredients. In a small bowl, whisk almond flour, sweetener, cinnamon, baking powder, and salt until no lumps remain.
Add the wet ingredients. Whisk in the egg and vanilla until smooth. Stir in the mozzarella.
If you want a more tender, donut-like center, add the heavy cream.
Grease the iron. Lightly spray or brush the waffle plates with oil or a bit of melted butter.
Cook the first chaffle. Spoon half the batter onto the hot iron, spreading just to the edges. Close and cook for 3–4 minutes, until deeply golden and crisp at the edges. Avoid opening early.
Repeat. Remove the first chaffle and set it on a rack to stay crisp.
Cook the second chaffle with the remaining batter.
Make the topping. Mix the granulated sweetener and cinnamon in a shallow dish. Brush each hot chaffle lightly with melted butter, then dip or sprinkle with the cinnamon-sweetener mixture.
Optional glaze. For a donut-shop finish, whisk powdered sweetener, cream, and vanilla until smooth. Drizzle over warm chaffles and let it set 1–2 minutes.
Serve. Enjoy warm as-is, or add berries, a dollop of whipped cream, or a pat of butter.