Add the zucchini and season lightly with salt. Cook the onions and zucchini, stirring occasionally, until the zucchini is soft, 3 to 4 minutes.
Add the beaten egg mixture (be sure that the mixture is smooth-no hunks of egg white). Using a small, heatproof rubber spatula, stir the zucchini mixture throughout the eggs. Don't worry about messing up the eggs, they will smooth out. Tilt the pan to allow the uncooked egg mixture to run to the sides of the pan to create a wide, flat "scrambled egg". Swirl the pan around occasionally to loosen the eggs from the bottom of the pan.
When the eggs are three-quarters of the way cooked through, sprinkle the middle third of the omelet with the grated fontina and most of the chives (save some chives for garnish). Turn off the heat.
Gently shake the pan to be sure that the omelet is loosened from the pan. Gently lay the right third of the omelet down on a serving plate and flip the other 2/3 of the omelet on top. The omelet should be folded like a letter.
Garnish the top with the remaining chives and serve with Mesclun Salad with Balsamic Vinaigrette.
When the mixture starts to look smooth and velvety, the oil can be added a little bit faster. Continue this way until all the oil has been added. When done, it should look very smooth, shiny, and homogeneous.
Add the garlic and season with salt. Taste it, it should taste good! Season with salt again, if needed.
To assemble the salad: Toss together the mesclun, cukes, tomatoes, and onions. Dress lightly with the vinaigrette. (You will not need to use all the dressing you made. Store the extra in the fridge and bring to room temperature when ready to use.)
Season vinaigrette with salt, if needed. Taste! The salad should be very flavorful but not soggy.
Plate the salad, piling it up so the lettuce looks fluffy and healthy and is adorned with the veggies. Using a veggie peeler, shave the cheese on top.