To make Spätzle, mix the flours, salt and nutmeg in a medium bowl. Add the eggs, most, but not all, of the water and start to whisk the batter. Add a little more water until the batter is like a thick pancake batter (thick but somewhat runny).

Make the spätzle in 3-4 batches. You can do it with a spätzle press, or by pressing the batter through a large-holed colander or tray like I'm doing in the photo. You can also use a cutting board by putting some batter at the edge of the board and cutting little pieces off with a knife directly into the boiling water.

Let the spätzle boil for a minute or two until they float up to the top. Scoop them out with a draining spoon...

And put into the bowl of warm warm. Continue to cook the remaining batches of spätzle, transferring each batch to the bowl of water when done.

While the spätzle are cooking (or afterwards), you can also start to saute the onions and mushrooms. Melt butter in a saucepan or frying pan and add the sliced onions and mushrooms.

Saute on on medium low until the onions are very soft and translucent. Add the heavy cream if using and simmer for 2-3 minutes. Turn off heat and add a sprinkle of salt and pepper to taste.

Drain the spätzle well and mix into the onion and mushroom "sauce" along with the parsley. Taste a little and add more salt and pepper if needed.

Transfer the spätzle to a casserole dish, and lightly mix in about 2/3 of the cheese so it's evenly distributed. Use the last 1/3 of the cheese to sprinkle over the top.

Put in the preheated (180°C/350°F) and bake for 15-20 minutes, until the cheese is melted and just a little browned on top (more or less to your preference).