Whisk eggs, milk, mustard, salt, pepper and nutmeg in a medium sized bowl.

Slowly stir the flour into the wet ingredients until the batter is smooth. The consistency should be halfway between that of pancake batter and pasta dough.

Let the batter rest at room temperature for at least 30 minutes or as long as an hour.

While the batter is resting, set a pot of salted water to boil. The pot you choose should be a bit smaller than your colander so that you can set the colander over the pan without it touching the water.

Once the batter has rested and the water boiled, set your colander over the pan and pour the batter into the colander. Using a rubber spatula push the batter through the holes and into the water. This process will take a little elbow grease.

The spaetzle will first sink to the bottom of the pan and then rise to the top. Once it has risen to the top, let it cook for another two minutes and then remove them with a skimmer and shock them in cold water and drain them well and set aside.

Melt one tablespoon of butter in one tablespoon of olive oil. Sweat the onions for 3-4 minutes and then add the mushrooms and sauté them until slightly brown. Add the spinach and let it wilt slightly.

Add the speatzle to the pan and stir completely. There should be enough fat in the pan to coat all spaetzle, so if there is not enough, add a bit more butter. Allow the speatzle to get a bit crispy in spots and be completely heated throughout.

Serve immediately.