In a large bowl, mix the rolled oats with water or milk.
Cover and let soak in the refrigerator overnight. The oats should absorb all the liquid and soften.
Birchermüesli (or Bircher muesli) is not just ordinary oatmeal. Dr. Bircher-Benner's original recipe was intended as a healthy dinner for patients, but it quickly spread and became a globally popular breakfast. The base is an overnight soaked mixture that does not contain yogurt, but rather condensed milk or cream and freshly grated apples.
In a large bowl, mix the rolled oats with water or milk.
Cover and let soak in the refrigerator overnight. The oats should absorb all the liquid and soften.
In the morning, add the freshly grated apples (with the skin on, but cored) to the soaked oats.
Stir in the lemon juice, hazelnuts, and cream or condensed milk. Mix thoroughly.
If desired, you can sweeten with honey or maple syrup, although the traditional recipe does not use sugar.
Divide the Birchermüesli into bowls.
Top with fresh fruit of your choice (e.g., raspberries, blueberries, or banana slices) and sprinkle with more nuts. Serve immediately.