Pour the sour milk into a clean dishcloth and drip off the thin liquid. Let the sour milk drain for a couple of hours until you get a lightly fluid consistence with about 1.3-1.5 l remaining.
If you want a thicker consistence (like cream cheese), drain the sour milk for about 4 hours.
Eat the drained sour milk with plum compote and toasted oatmeal for breakfast.
Toasted oatmeal: Toast the oatmeal flakes in a frying pan until crisp and golden.
Add honey, butter and salt to the pan and stir well with a wooden spoon until the oatmeal is caramelized.
Pour the toasted oatmeal flakes into a tray and let them cool.
Rinse the plums well and pour them into a pot with sugar and the water clinging to them.
Boil the plums, until they soften and the pits start appearing.
Filter the compote in a course sieve when it is fully cooked, so the pits remain in the sieve. If the compote is too thin, boil it in a pot, stirring constantly, until it reaches the right consistency.