In a small bowl or cup, thoroughly whisk together eggs and small pinch of salt (I prefer black truffle or wild porcini salt, but you may use plain salt.) Set aside.
In a small nonstick skillet, over medium heat, melt butter.
Add julienned zucchini and/or yellow squash; saute for approximately one minute, until just beginning to lightly brown.
Add thinly sliced spring onion; saute until vegetables are soft and lightly browned.
Pour beaten eggs evenly over the veggies.
Sprinkle with 1/2 of the chives; cook over medium/medium-low heat until eggs are mostly set, yet slightly jiggly/loose on top.
Sprinkle evenly with mozzarella and asiago cheeses and bacon bits (if using.)
Working from one side to the other, use a spatula to lift the edge and turn 1/3 of the omelette toward the center; place spatula under omelette and fold over onto remaining edge; slide onto warm serving plate.
Sprinkle with remaining chives and a bit of grated cheese and bacon bits, if desired. Serve hot or warm.