Joy the Baker raised a crucial point about breakfast a few years ago. Most breakfast recipes out there can't be scaled to feed just one. Even if you add just one egg, you will end up with way too much batter for crepes or pancakes. Joy solved the problem with pancakes, and possibly waffles with her iconic post titled The Single Lady Pancake.
I've now encountered a similar problem with birchermuesli. A Swiss breakfast staple, bircher is a delicious combination of uncooked oats left to soak overnight, apples, nuts and dried fruits. The issue here is the apple. Even the smallest apple will be too much for one serving and you can't leave these apples lying around, they brown too quickly.
So here's my solution. The night before, measure out 3 tbsp oats in a large bowl. Add enough apple juice to cover the oats. This will impart the traditional apple flavour to your bircher without you grating a real apple. The next morning, pick a fruit that goes with oats. It has to be something sweet, not tart and preferably small enough to scale down. Ideal, as you can see, will be grapes. Or berries. Add that to your oats and then anything else that catches your fancy. I like the bite of nuts so I added almonds and then some cranberries to make it an indulgent breakfast. Mix it all in and if you find the muesli to be too thick, you can add a bit more apple juice or even some yogurt.