Add water, bay leaf, peppercorns, salt, roughly-cut soup greens, and quartered onion to a large pot. Bring to a boil over high heat.
Add veal and pork to the boiling broth. Reduce heat to low and simmer for roughly 40 minutes until the pork reaches 63 °C (145 °F) and the meat is tender.
Remove the meat from the broth with a slotted spoon and let cool to room temperature. Once cool, cut into cubes.
Pour the broth through a sieve into a bowl. Measure out 3/8 liter (roughly 375 ml) of the strained broth.
Season the measured broth with 125 ml vinegar, salt, and sugar to taste.
In a small bowl, mix the ground gelatin with 5 tablespoons of cold water. Let sit for 10 minutes to swell.
Heat the seasoned broth over high heat until boiling. Add the swollen gelatin and stir constantly for 2-3 minutes until completely dissolved.
Stir the meat cubes into the hot broth with dissolved gelatin. Pour the mixture into a cold-rinsed dish or individual coffee cups.
Refrigerate for at least 4 hours until the aspic is firm and set.