In a bowl, whisk together the eggs, milk, salt, and pepper until well combined.

In a non-stick skillet over medium heat, melt half the butter. Add the mushrooms and garlic, sautéing until tender (about 5 minutes). Remove and set aside.

Wipe the skillet clean and return to medium heat. Melt the remaining butter, making sure it coats the entire pan.

Pour in the egg mixture, tilting the pan to spread it evenly. As the eggs set, lift the edges with a spatula, allowing uncooked egg to flow underneath.

When the omelet is almost set, sprinkle the Swiss cheese and sautéed mushrooms over one half of the eggs.

Using a spatula, fold the other half of the omelet over the filling. Cook for another minute or until the cheese melts.

Slide onto a plate, garnish with fresh herbs if desired, and serve immediately.