Combine the egg yolks, milk, and some salt/pepper in a small bowl. In the bowl of a stand mixer or in a mixing bowl using a handheld mixer, whip the egg whites until they’ve got stiff peaks. Fold the milky yolks into the whites, being careful not to deflate them.
Add the butter to a large non-stick skillet over medium heat. Pour the egg mixture into the pan in an even layer and allow it to cook and set; about 3 to 4 minutes or so. To one half of the pan, add the brie, sun dried tomatoes, and spinach and cover the pan with a lid (this will help the top set).
Flip one half of the omelette over (the half with no fillings) on top of the other, and allow your omelette to cook for a couple/few minutes more. I like to lift the omelette up to make sure the bottom isn’t getting too dark.
Transfer the finished omelette to a serving plate and drizzle with honey, if desired. Enjoy right away.