Белые грибы можно засушить.

Because it describes грибы, which is plural. In Russian, adjectives agree with the nouns they modify in number, gender, and case.

• белый гриб = a porcini mushroom / a white mushroom
• белые грибы = porcini mushrooms

Here both words are plural:

• белые = plural adjective
• грибы = plural noun

Usually it means a specific kind of mushroom: porcini (also called cep in English).

So in many contexts, белый гриб / белые грибы is not just a literal description of color. It is the normal Russian name for porcini mushrooms.

That said, grammatically it still looks like an ordinary adjective + noun combination, so without context a beginner might read it literally as white mushrooms.

Because Russian often uses the impersonal construction можно + infinitive.

• можно = it is possible / one can / you can
• засушить = to dry (something) thoroughly, usually for preservation

So Белые грибы можно засушить means something like:

• Porcini mushrooms can be dried
• You can dry porcini mushrooms
• It is possible to dry porcini mushrooms

Russian does not need to name the person doing the action here.

Можно creates an impersonal idea: it is possible, one can, it can be done.

• Белые грибы можно засушить = porcini mushrooms can be dried
• Белые грибы могут засушить would mean porcini mushrooms may dry something or are able to dry something, which makes no sense because the mushrooms would become the subject doing the action.

So можно is the natural choice when English uses can be ....

Not really, even though in English we might translate it that way.

In Russian, the core structure is:

• можно засушить = it is possible to dry
• белые грибы = the thing being dried

So logically грибы is the object of засушить.

However, because грибы is inanimate plural, its accusative plural form is the same as its nominative plural form:

• nominative plural: грибы
• accusative plural: грибы

So it looks like a subject form, but here it functions as the object.

Засушить means to dry something thoroughly, usually so that it keeps well. It often suggests drying for preservation.

For example, mushrooms, herbs, flowers, or fruit can be засушить.

It is related to сушить:

• сушить = to dry, to be drying (imperfective)
• засушить = to dry completely / to dry for storage or preservation (perfective)

So in this sentence, засушить is very natural because mushrooms are often dried and stored for later use.

Russian often uses можно + perfective infinitive when talking about the possibility of achieving a result.

• можно засушить = can be dried successfully / can be dried and preserved
• можно сушить = can dry / it is allowed or possible to be drying

So the perfective засушить focuses on the completed outcome, which fits the idea well: the mushrooms can be dried and kept.

If you said Белые грибы можно сушить, it would not be impossible, but it would sound more like talking about the process in general, not the finished preserved result.

Both can often be translated as to dry, but the nuance is a little different.

• высушить = to dry out, to make dry
• засушить = to dry thoroughly, often for preservation

With mushrooms, засушить is especially natural because drying mushrooms is a common way to preserve them.

So:

• Белые грибы можно засушить sounds very idiomatic.
• Белые грибы можно высушить is also possible, but it may sound a little more neutral and less specifically about preservation.

Because Russian often prefers an impersonal active structure where English uses the passive.

English:

• Porcini mushrooms can be dried.

Natural Russian:

• Белые грибы можно засушить.

A more literal passive version is possible, for example:

• Белые грибы могут быть засушены.

But that sounds more formal, heavier, and less natural in everyday speech. The можно + infinitive construction is much more common.

Yes. Russian word order is flexible.

These are all possible:

• Белые грибы можно засушить.
• Можно засушить белые грибы.

The meaning stays very similar, but the focus changes a little.

• Белые грибы можно засушить puts белые грибы first, so they are the topic: As for porcini mushrooms, they can be dried.
• Можно засушить белые грибы starts with the possibility/action: You can dry porcini mushrooms.

The original sentence sounds very natural.

Russian has no articles. So белые грибы can mean different things depending on context:

• porcini mushrooms in general
• some porcini mushrooms
• the porcini mushrooms

In this sentence, it most naturally means porcini mushrooms in general.

Yes, можно can express both possibility and permission, depending on context.

But in this sentence, the most likely meaning is possibility or practical option:

• Porcini mushrooms can be dried
• You can dry porcini mushrooms

If the context were about rules, then можно could mean it is allowed.

A rough pronunciation guide is:

BYE-ly-ye gree-BY moozh-nuh zuh-soo-SHEET

A few helpful points:

• Белые sounds roughly like BYE-ly-ye
• грибы has stress on the second syllable: gree-BY
• можно is pronounced roughly MOZH-nuh
• засушить has stress on the last syllable: zuh-soo-SHEET

Stress is important in Russian, especially for vowels.