Should sensual pleasure be actively avoided, rather than simply not sought? I am particularly interested in regards to taste

The Buddha never asked us to avoid certain things for fear of getting attached. He never asked us to close our eyes so that we don't see beautiful things. Instead, what the Buddha said was to train your mind so that you don't get attached to these things.

So with the noddles, I think it's ok for you to put the flavour packet in and have a tasty meal, but while you're eating, eat it mindfully. Make sure that you don't cling to it, remember that the taste is impermanent etc.

You can also practice 'Asubha' with regards to food if you're very attached to this taste. You can think that this taste only lasts momentarily whilst it's in my tongue. After that point, you don't feel any taste at all. And imagine what happens to this food after it goes into the body and digests itself. So in that way, you can try to reduce and control your craving/ clinging to this taste, and still have pleasant meals.

The scriptures tell us that all beings subsist on food. So we have to eat. But there is a big difference between live to eat and eat to live. That’s why there is a precept for monks against eating after noon or before dawn. It is there for them to not give into pleasures of taste. So it is OK to taste the tastes, but being mindful about is, as in how Buddha advised Mahànàma, on how does the noble disciple partake food reflecting? .

The discourse “where there is passion” in Samyutta Nikaya or Atthi Raga Sutta Buddha says that there are four kinds of nutriments. One is material or physical, while the other three are mental nutriments. It is important that we understand these four nutriments clearly to understand how they nourish us resulting in rebirth. Also it will answer your next question. Of course you should add the flavour. Also you should have the full awareness when you taste the flavour. This is how my teacher, Ven. Kiribathgoda Gnanananda Thero, explained it:

” To understand this factor, I will explain in this manner. Our consciousness is with the physical food we consume. For example, do we have a desire for food? Yes, we have. Do we not derive pleasure from what we eat? Yes, we do. Do we have a passion for what we eat? Yes, we do. Thus our mind is attached to the food. When our mind is attached, consciousness arises and grows. It grows like a tree. Therefore the cause for the growth of consciousness is passion, delight or pleasure and craving. When consciousness arises, mentality-materiality (nama rupa) alights. We will try to understand what this means in the following manner. For example, we see some tasty food. Then what happens in our mind? The food was something that we saw from our eyes. What happens next? We develop a desire to consume it. Therefore desire for taste has arisen. Then what happens? We feel like buying it, to cook it, to taste its flavour. What has grown is consciousness. When consciousness arises, mentality-materiality is established. When we see some tasty food or think of food, there is secretion of saliva. What does it mean? It is a reaction in our body - contact and feelings have arisen automatically. There are six factors that manifest itself. The four elements that constitute our body - the material phenomena (rupa); contact (phassa), feeling (vedana), perception (sanna), volition (cetana) and attentiveness (manasikara).”

”If you think carefully you would realize this happens when our thoughts are with food. As we think of food, before we could flutter an eyelid, desire for food arises and consciousness is established. Then mentality-materiality alights. Where mentality-materiality alights, there is the growth of fabrications resulting in the ‘kamma’ process, and thus renewed becoming and rebirth results. Birth results in ageing, sickness and death, and sorrow, lamentation, pain, grief and despair.”

”In the same way the Tathagatha has explained the nutriment of physical food to be regarded. It should be for sustenance and not for its passion, delight or desire. To cultivate one’s mind in this manner is difficult but not impossible. In the modern world we are often misled by the propaganda to promote the sale of various kinds of food. The mentality of our society is to satisfy man’s senses and desires. Food advertis*m*nts often rouse our desires and they do not show reality. That is why the Buddha said when one consumes food one should not think that the food consumed is to gain strength, sensual desire or to be athletic. We should consume food with the thought that it is for sustenance. This would help in our moral training and would also help in the development of mindfulness. We should think that food is subject to change, is impermanent, it gets spoilt and perishes. Then the desire, craving for food will not arise. Then we would learn to be mindful that all conditioned things are impermanent (anicca).”

I think that's an advanced/difficult question.

In summary I think it's recommended that you to avoid becoming 'attached' to sensual pleasure[s]. Seeking (sensual) pleasure (i.e. 'thirsting' or 'craving' for pleasure) might be a symptom of and a precursor to being attached to it. And 'contact' with objects, from which arise 'feelings' of pleasure, might lead to 'craving' and 'attachment'.

I think the above is part of the theory of the Twelve Nidānas (sense base -> contact -> feeling -> craving -> attachment).

I'm not sure but maybe theoretically you can break the chain anywhere: if you avoid contact for example then it doesn't arise; or if you have contact but avoid feeling; or etc.

Food is a difficult subject partly because (unlike sex, drugs, music, money) it isn't possible to avoid contact.

I guess that to the extent that monastics eat what they're given, they don't choose it and so it's easier to see it as uncontrolled/non-self/impermanent -- not a karmic act maybe (not an act of will) -- nothing to worry about (though this about "not worrying" is more-or-less idealistic on my part -- in practice they cope with hunger).

Another reason why I assume that this topic is difficult is because, according to the Four stages of enlightenment, "freedom from sensual desire" is associated with one of the last two stages.

Here is an annotated version of the Sekha Sutta (which Saptha Visuddhi's answer recommended). It begins to explain terms like "one whose sense-doors are guarded". Even so it might require more to understand, for example it says "he grasps neither its sign nor its detail" which supposes you understand the word "sign" (which is annotated in a footnote but also mentioned in the introduction to this Sutta Discovery essay).

It's possible that you'll find basic teaching helpful: "Thinking about food but don't get attached to the thought, let it go, keep breathing" or "This is the arising of stress, and the cessation of stress" or "Not me or mine" etc.

You mentioned "mortification" but, in English anyway, I think that means literally "putting to death" i.e. it's an extreme. Foregoing a useless snack isn't necessarily it. I think the theory is that by avoiding attachment/craving for sensual pleasure you can avoid suffering and find a more lasting ease. Mortification is wrong but (for monks, more or less 'advanced') something like disillusionment/revulsion (Nibbidā) is recommended in various of the Pali suttas.