Combine milk, eggs, and nutmeg in processor; blend until smooth, about 30 seconds. Add salt and flour pulsing until batter is just smooth, about 30 seconds (batter will be very thick and sticky).
Working in batches, pour batter through slotted spoon or grater held above boiling water, pressing with spatula to form strands. Stir gently to prevent sticking. Simmer until spaetzle float to surface, then continue cooking 1 minute longer.
Using slotted spoon, transfer spaetzle to large buttered baking dish. (Can be made 2 hours ahead. Let stand at room temperature.).
Cook butter & sage in heavy large skillet over medium heat until golden brown, about 3 minutes. Add spaetzle and toss until heated through. Season to taste with salt and pepper.
Divide among plates.
Garnish with fresh sage.
Optional: Sauteed 1 small onion diced in the butter.