How to Make It
In a large bowl, mix the flour with the salt and make a well in the center. Add the eggs to the well and lightly beat them. Whisk the flour into the eggs. Gradually whisk in the milk until a very thick batter forms. Cover the bowl with a damp cloth and let stand for 30 minutes.
Meanwhile, in a large nonstick skillet, melt 2 tablespoons of the butter. Add the panko and cook over moderately high heat, stirring, until golden, about 3 minutes. Transfer the crumbs to a plate and wipe out the skillet.
Bring a large pot of salted water to a boil. Working in batches, using a wet spoon, scoop heaping teaspoons of the batter into the boiling water. Once the spaetzle rise to the surface, boil them until they're cooked through, about 2 minutes. Using a skimmer or a slotted spoon, transfer the spaetzle to a platter. Repeat with the remaining batter.
Melt 2 tablespoons of the butter in the large skillet. Add half of the spaetzle and cook over moderately low heat for 4 minutes, tossing gently. Transfer the spaetzle to the platter; repeat with the remaining butter and spaetzle. Sprinkle the bread crumbs over the spaetzle and serve.