I made this up based on what I had left in the cupboard - it's fully customizable.
Swapping standard orange juice for tart apple cider shifts the foundational flavor profile from tropical brightness to autumn-crisp acidity, directly altering how the starches interact with the liquid. Originally developed in Switzerland around the turn of the twentieth century as a dietary raw-food dish by physician Maximilian Bircher-Benner, this formulation relies entirely on hydration rather than applied heat to soften raw oats and grains. Soaking the dry components for at least eight hours allows the starches to fully absorb the surrounding moisture, softening the outer bran layers without dissolving the structural integrity of the individual flakes. When utilizing fresh grated fruit instead of bottled juices, enzymatic activity releases natural pectins that thicken the surrounding dairy, whereas pasteurized liquids result in a thinner, more pourable consistency upon stirring. This basic single-serving ratio scales upward easily for meal preparation, though batches exceeding four portions require careful liquid measurement adjustments to prevent uneven softening across the bottom layers of the container. Incorporating frozen berries introduces localized pockets of moisture as the ice crystals melt into the surrounding oats, creating marbled streaks of color and concentrated tartness that contrast sharply with the mellow base. Maintaining a chilled storage temperature between thirty-four and thirty-eight degrees Fahrenheit throughout the overnight soaking phase ensures food safety when dairy and fresh juices are combined for extended periods. Final texturing depends entirely on the addition of yogurt just before consumption, which coats each softened grain with milk fats and adds a rich, tangy counterweight to the sweet fruit juices.