Утром мне хочется не столько кофе, сколько тёплой каши.

Утром is the instrumental singular form of утро. In Russian, the instrumental case is often used by itself to express time, especially parts of the day:

• утром = in the morning
• днём = in the daytime / during the day
• вечером = in the evening
• ночью = at night

So Russian does not need a separate word like in here.

A useful contrast:

• утром = in the morning, this morning, mornings in general depending on context
• по утрам = in the mornings / every morning, more clearly habitual

Both can be translated with want, but they are not exactly the same.

• я хочу = I want
• мне хочется = I feel like..., I would like..., I’m in the mood for...

Мне хочется sounds softer and more spontaneous. It often describes a feeling or craving rather than a firm, deliberate wish.

So in this sentence, мне хочется suggests something like: in the morning, what appeals to me is warm porridge rather than coffee.

Хочется is the present-tense form of хотеться, which is an impersonal verb meaning to feel like, to want, or to be in the mood for.

It is called impersonal because Russian does not treat the person who has the desire as the grammatical subject. Instead, that person appears in the dative:

• мне хочется = I feel like / I want
• тебе хочется = you feel like
• ему хочется = he feels like

That is why you get мне, not я.

The -ся is just part of the verb хотеться. It is related to хотеть, but it is a different verb with a different structure and nuance.

This is a very common Russian pattern meaning:

• not so much X as Y
• not so much X, but rather Y

So:

• не столько кофе, сколько тёплой каши

means the speaker is contrasting two things and saying that the second is more desired than the first.

An important nuance: this does not necessarily mean the speaker rejects coffee completely. It means coffee is not the main thing they want; warm porridge is.

Because не столько ..., сколько ... is a paired correlative construction. Russian normally puts a comma before the second part, just as English would usually separate not so much X as Y with a pause.

So the comma marks the contrast between the two compared items:

• не столько кофе, сколько тёплой каши

After хочется, Russian very often uses the genitive case for the thing desired, especially with food, drink, or something wanted in an indefinite amount.

So:

• хочется каши = I feel like some porridge
• хочется чаю / чая = I feel like some tea
• хочется супа = I feel like some soup

Here, каши is the genitive singular of каша.

This often has a partitive or indefinite sense: not the porridge as a specific object, but some porridge.

Because adjectives must agree with the noun they describe in case, number, and gender.

Here the noun is каши, which is:

• feminine
• singular
• genitive

So the adjective must also be feminine singular genitive:

• тёплой каши

Compare:

• nominative: тёплая каша
• accusative: тёплую кашу
• genitive: тёплой каши

Because кофе is an indeclinable noun in standard Russian: its form usually stays the same in all cases.

So even if it is functioning here the same way that каши is, its form does not visibly change.

Also, standard Russian traditionally treats кофе as masculine:

• горячий кофе
• крепкий кофе

In modern colloquial speech, some speakers also use it as neuter, but for learners, masculine is the safest standard choice.

Yes, functionally it is understood the same way as the second noun phrase after хочется. The difference is just that кофе is indeclinable, so you cannot see the case ending.

So the contrast is essentially between:

• кофе
• тёплой каши

The second one shows the genitive ending clearly, while the first one does not show it because the word form stays the same.

Yes, Russian word order is flexible. This order is natural because it starts with the time frame:

• Утром = in the morning

Then it gives the experiencer:

• мне = to me

Then the predicate:

• хочется

This is a very normal flow in Russian: set the scene first, then say who experiences the feeling, then say what the feeling is.

Other orders are possible, but they would shift emphasis. For example:

• Мне утром хочется... puts slightly more focus on me
• Не столько кофе, сколько тёплой каши, мне хочется утром is grammatical, but much less natural in ordinary speech

So the original order is the most neutral and idiomatic.