Name: What to Do With Leftover Egg Whites: Fluffy Vegetable Omelette
Prep time: 5 min
Cook time: 10 min
Total time: 15 min
Yield: 1 large omelette
Ingredients: 6 egg whites (about 180ml / ¾ cup); 1 whole egg (optional, for colour and richness); 1 tbsp olive oil or butter; 1 small onion or 2 spring onions, sliced; 1 cup / 150g quick-cooking vegetables — peppers/capsicum, courgette/zucchini, mushrooms, tomatoes, or spinach; 40g / ⅓ cup grated cheese — cheddar, feta, or whatever is open; A handful of soft herbs, chopped; Salt and black pepper

You made custard, carbonara, hollandaise, or mayonnaise, and now there are five egg whites in a jug. The good news about what to do with leftover egg whites is that you have two genuinely reliable options: freeze them for later, or turn them into a light vegetable omelette in fifteen minutes tonight.

Meringues and macarons are the famous answers, but they are a project. This is the weeknight one.

Freezing is the best default

Egg whites freeze better than almost anything else in the kitchen, and they lose nothing in the process. Pour one white into each compartment of an ice-cube tray, freeze until solid, then transfer the cubes to a bag and label it with the count and the date.

Thaw them overnight in the fridge and use them as you would fresh — including for meringue, which still whips properly after freezing. Use within about 12 months.

Cooking whites without making rubber

Egg whites behave differently from whole eggs because they have no yolk fat. That means they stick more, set faster, and turn squeaky if you push them.

Three things fix it: a non-stick pan, a heat setting one notch lower than you would use for a normal omelette, and stopping the moment the top is set. Adding a single whole egg to a batch of whites also makes a real difference to texture and colour, if you have one to spare.

Use up the fridge while you are at it

The vegetables here are entirely open. Whatever is soft, wilting, or nearly gone belongs in this pan — mushrooms, peppers/capsicum, courgette/zucchini, tomatoes, the last of a bag of spinach, or the herbs starting to go limp in their packet. Firmer vegetables go in first; leaves and tomatoes go in at the end.

Food safety with raw whites

Keep leftover raw whites in a covered container in the fridge and use them within two to four days, or freeze them. Do not taste the raw mixture, and cook the omelette until there is no runny egg left. If the whites smell off or have changed colour, discard them.

Where the yolks went

If you have the opposite problem, a batch of spare yolks enriches custards, pasta sauces, and mayonnaise. And if you simply have a lot of ordinary eggs to get through, what can I make with eggs covers the flexible frittata that handles almost any combination. Leftover soft herbs from either can become a green herb sauce rather than going in the bin.

How to make it

Whisk the egg whites with a good pinch of salt and pepper until loose and slightly frothy, about 20 seconds. Whisk in the whole egg if using.

Warm the oil or butter in a 24cm / 10 inch non-stick frying pan over medium heat. Cook the onion for 3 minutes until softened.

Add the firmer vegetables and cook for 3–4 minutes, until just tender. Add spinach or tomatoes for the last minute.

Spread the vegetables into an even layer and turn the heat to medium-low. Pour in the egg whites.

Cook undisturbed for 4–5 minutes, drawing the set edges gently towards the middle once or twice so the liquid runs underneath.

Scatter over the cheese and herbs. Cover the pan for 2 minutes, or slide it under a hot grill/broiler, until the top is set with no runny egg remaining.

Slide onto a board, cut in half, and season again to taste.