Why should you add ingredients one by one in a pan fry (for fajitas)?

Question

I’m trying to make classic, straightforward fajitas. I’m new to this and an amateur.

The recipe I’m currently trying is, slicing chicken, white onion, and red and yellow bell peppers. I’ll pan fry it in vegetable oil. I’ll use cumin, chili powder, garlic powder, and pepper (and salt). I’ll fry it on medium-high heat.

My question is, it generally seems like people add ingredients one by one, in any similar pan-fried / sautéed dish.

I am looking for a deep answer as to if this is genuinely much better than frying all at once, and why.

For example, I know different ingredients have different cooking times. But sometimes in some recipes, I think people sometimes vary in if they do onions first, then meat; or meat first, then onions.

Does this mean that somehow, when one ingredient is already cooked, when you put in the next ingredient, the cooking somehow applies more to the fresher ingredient, and the already cooked one can kind of remain at the same status, somehow? I’m thinking maybe it’s because the new ingredient releases a lot more water so the other ingredient absorbs or cooks in the water so it’s not at risk for burning or overcooking or something?

But I mean, what if you did meat and onions at the same time? Is the problem that they are both releasing water and preventing each other from getting browned to the right amount?

I also feel like at lower and higher temperatures sometimes you don’t have to worry about difference in cooking time. When you slow cook at low temperatures, it seems like ingredients tend to fall apart and lose temperature less. So you can cook everything at once because they will not overcook anyway. Whereas at high temperatures it’s sort of the opposite, searing everything on the outside activates flavor and juices, while the insides may remain moderately or only medium cooked. So again, maybe order doesn’t matter, since they’re all getting like flash seared on the outside.

So, what is the nature of the order of putting in ingredients, depending on temperature, beyond the obvious aspect of them having different cooking times? Is cooking in isolation beneficial for flavor and carmelization?

Answer 1

You are considering all the right things here, and I would encourage you to keep observing and experimenting as you cook to help develop your intuition. The key points are:

• Some of the cooking reactions you want require a high temperature: in particular browning of meat and vegetables.
• A 'crowded' pan cannot easily reach those high temperatures, because the ingredients you are cooking with contain water and if there is no space for that water to evaporate then the temperature gets stuck at 100°C.
• Some food items release more water than others, especially some vegetables and meat (and meat quality matters a lot here; cheaper meat is more likely to have more water in it).
• Different types of food have a greater risk of overcooking and becoming less tasty – the most obvious example here is if you are cooking with chicken breast it is easy to overcook it, whereas chicken thigh will be affected less by longer cooking. Spices and things like garlic are also affected by cooking time.

As an example – which I don't claim to be the 'correct' way to do things, here is how I would think about your fajita example:

• Chicken first, because I want it to brown in the pan and it won't brown well once there are vegetables with moisture in. If I'm using chicken thighs then once they are brown I'll push them to the side, if chicken breasts then I'll take them out and keep them in a bowl while I do the rest.
• Onion and peppers next, which will soften and get some colour (which means 'start to brown') as long as my pan is hot and large enough. I might put a lid on to help them soften, because it traps the hot steam inside.
• When the vegetables are nearly done, I'd add the spices and garlic and fry them a little; that helps develop the flavour (especially if using raw garlic) and mix it into the oil, so it can spread onto the chicken and vegetables better. I can add the chicken back in if I took it out.