In a bowl, whisk together the flour, eggs, milk, and salt. Stir until the batter is well combined and develops bubbles. Let rest 5-10 minutes.
Put a colander into a bowl to drain the Spätzle once cooked and bring a large pot of water over high heat to a boil, add about 1 tbsp of salt to the water, and reduce temperature to a simmer.
Work in batches using roughly one-third of batter at a time. Cook until they float (2-3 minutes), stirring occasionally. Transfer to colander with a slotted spoon.
Serve the Spätzle immediately or sauté them in butter to crisp them up a little. Add 1-2 tablespoons butter if holding to prevent sticking.
Notes
Clean equipment immediately with cold water; hot water makes dried dough cement-like.
Store leftovers tossed with butter/oil in airtight container for 3-4 days; reheat by sautéing.