I used to think that truly authentic bircher muesli—the kind I ate as a kid at my great-aunt's home in Oftringen, Switzerland—wouldn't be possible without whole milk or yogurt. But homemade, unstrained macadamia milk creates a perfect base for this sweet, rich, and comforting breakfast. —Gena Hamshaw
Combine all ingredients in a glass mixing bowl. Cover and transfer to the fridge. Allow to sit overnight. In the morning, divide the muesli into bowls and serve, with a drizzle of maple syrup if desired.