In a large bowl, combine eggs, milk, salt, and pepper. Add flour a 1/2 cup at a time. Stir with a wooden spoon until smooth. Let rest 10-20 minutes. The dough should be like pancake batter – thin with more milk if necessary.
Meanwhile, saute onion in butter until golden. Set aside.
Preheat oven to 350. Drop nocken through the holes in a sieve (see techniques) into simmering water. Cook until the nocken float.
Remove the nocken from the water with a strainer. Place in a buttered casserole or oven-safe pan.
Sprinkle with grated cheese and caramelized onion. Bake for 15-20 minutes. Serve out of pan.