Whisk together the egg yolks and cream or milk. Season with salt.
In a separate bowl, beat the egg whites with salt and lemon juice until stiff peaks form.
Gently fold the beaten egg whites into the egg yolk mixture until well combined. If using, fold in the goat cheese.
Heat olive oil in a pan or cast iron skillet over medium heat.
Place the asparagus and green onions in the pan, all facing the same direction, and cook for 1 minute.
Pour the egg mixture over the asparagus and green onions.
Cook until the omelette is puffed and golden on the bottom, about 5-7 minutes.
If using, crumble goat cheese over the top of the omelette.
Carefully fold one side of the omelette over using a large spatula.
Remove from the pan and garnish with microgreens, additional asparagus, and sea salt. Serve warm.