Preheat the oven to 180°C (or preheat an air fryer to the same temperature). Lightly grease a small oven-proof dish.
Place the cottage cheese in a bowl. Add the egg, sweetener, vanilla extract and half of the cinnamon, then mix until smooth and well combined.
Stir in the rolled oats, mixed spice and chopped chestnuts until evenly distributed.
Transfer the mixture to the prepared dish and smooth the surface.
Bake for about 15 minutes, until just set and lightly golden on top.
Allow to cool slightly before serving.
Serve warm or at room temperature, drizzled with extra honey or syrup if desired. A spoonful of Greek yoghurt or custard also works beautifully.