When it comes to retaining the nutrients in veggies, colors as well, the best cooking method there is to -- dry cook. That means, she could either stir-fry them ( fry them under the water vapor ) or grill them. Also, she can roast them. That way, the veggies will keep all the nutrients inside, the same is for color. The water that is a product of frying, grilling and roasting can be further used for making a soup and sauces.
An elaborate dish is a type of dish that needs to be made perfectly. In other words, we should stick to the recipe no matter what. It's very complex and we should stick to every written detail -- no improvisation and no risks. For example, if she wanted to replace an onion with a garlic, she should not do that as it would change the taste and the authenticity of it.
