Whisk together the flour, nutmeg, and salt in a large bowl.

Add the eggs and seltzer and knead into a dough.

Cover the bowl with a dish towel and let stand at room temperature for 1 hour.

Peel the onions and cut them into rings.

Heat the olive oil in a skillet. Add the onion rings and fry until golden brown. Remove the fried onions from the heat, cover to keep warm, and set aside.

Bring a large pot of salted water to a boil.

Use a spätzle press or colander with large holes to push the dough through into the water.

When the späztle pops up to the top they are done, use a slotted spoon to remove them from the pot and transfer to a colander or sieve to drain.

Preheat the oven to 350 degrees F.

Place the drained spätzle into a casserole dish. Toss with the walnuts and the cheese.

Place the dish in the oven and bake for 15 minutes.

Remove the spätzle from the oven. top with the fried onions. Scatter the chives on top and serve.