In a large bowl, whisk together the flour and salt, then add in the eggs along with the milk or water. Beat everything together until you get a thick, smooth batter, similar in texture to a heavy pancake batter. It should hold together without feeling runny or stiff like dough.
While your batter rests for a few minutes, fill a large pot with water and bring it to a rolling boil. Add a generous pinch of salt, just like you would for regular pasta, since this is your chance to season the spaetzle from the inside out.
Working in batches, scoop some batter into your spaetzle maker, or press it through a large-holed colander set over the pot. The little dumplings will drop straight into the simmering water and start cooking almost immediately.
The spaetzle will sink at first, then rise back up to the surface once they're fully cooked, which usually only takes a minute or two. Use a slotted spoon to scoop them out as soon as they float, transferring them to a colander to drain.
Melt butter in a large skillet over medium heat, then toss in your drained spaetzle. Sauté for a few minutes until they're lightly golden and coated in butter, which gives them a nicer bite and keeps them from sticking together before serving.