1. Stir oats, chia seeds, 1/2 tsp cinnamon, 1/4 tsp salt, and optional protein powder in a large measuring cup. Then whisk in milk, sweetener, and 3/4 cup of the yogurt.
2. Cover and refrigerate overnight, during which time the mixture will thicken considerably.
3. Meanwhile, dice the apples. Stir with the oil or water and remaining cinnamon, maple syrup, and salt in a saucepan or frying pan over medium heat.
4. Stir the sautéed apples frequently until soft, and add more water or oil if needed to prevent sticking.
5. When ready to serve, layer the apple cinnamon overnight oats, remaining yogurt, and cooked apples in mason jars or bowls. Enjoy hot or cold.
6. Store leftovers covered in the refrigerator for up to four days.