Prepare the Eggs: In a small bowl, combine the egg whites, water, salt, and pepper. Whisk gently with a fork until just combined and slightly frothy. Set aside.

Sauté the Aromatics: Heat the olive oil or butter in a 20-23cm non-stick frying pan over a medium-low heat. Add the minced garlic and cook for about 30 seconds until fragrant, being careful not to let it brown.

Cook the Vegetables: Add the halved cherry tomatoes to the pan. Cook for 2-3 minutes, until they begin to soften and release their juices. Add the spinach and cook for another 1-2 minutes, stirring, until it has just wilted.

Remove Fillings: Tip the cooked vegetable mixture out of the pan onto a plate and set aside. This prevents the omelette from being overstuffed and difficult to fold later. Give the pan a quick wipe with a paper towel.

Cook the Omelette: Return the pan to a medium-low heat. If it looks dry, add a tiny bit more oil. Pour the egg white mixture into the pan. Let it cook undisturbed for 1-2 minutes, until the edges begin to set.

Gently Scramble: Using a silicone or rubber spatula, gently push the cooked egg from the edges toward the centre. Tilt the pan to allow the uncooked egg to flow into the empty spaces. Continue this for 1-2 minutes until the omelette is mostly set but still slightly moist on top. What works best for me is keeping the heat low to avoid browning the bottom too quickly.

Add Fillings and Fold: Spoon the cooked vegetable filling and the crumbled feta over one half of the omelette. Cook for another minute to warm the fillings through and allow the cheese to get slightly melty.

Fold and Serve: Carefully slide the spatula under the empty side of the omelette and fold it over the filling. Let it sit in the pan for 30 seconds more, then gently slide it onto a warm plate. Garnish with fresh parsley or chives and serve immediately.