Ne pravim juhu od poriluka zato što je najjeftinija, nego zato što je baka uvijek tako kuhala.

It creates a correction or contrast:

Ne pravim juhu od poriluka zato što je najjeftinija, nego zato što je baka uvijek tako kuhala.

This means:

• not because X
• but because Y

So the speaker rejects one possible reason and gives the real one.

A very common pattern in Croatian is:

ne ..., nego ... = not ..., but rather ...

Here it works together with the two zato što clauses:

• Ne ... zato što ...
• nego zato što ...

So the whole idea is: not for this reason, but for that reason.

Because Croatian often drops subject pronouns when they are already clear from the verb ending.

Pravim already tells us the subject is I.

So:

• pravim = I make / I am making
• ne pravim = I do not make / I am not making

Adding ja is possible, but it usually adds emphasis or contrast:

• Ja ne pravim... = I’m not the one who makes... / As for me, I don’t make...

Without ja, the sentence sounds completely normal and natural.

It can mean either one, depending on context.

Croatian present tense often covers both:

• English I make
• English I am making

So Ne pravim juhu... could mean:

• I don’t make leek soup...
• I’m not making leek soup...

The surrounding context tells you which is meant. In this sentence, the meaning is probably more general: I don’t make leek soup for that reason...

Because juhu is the accusative singular form, and it is the direct object of pravim.

The base form is:

• juha = soup

But after a verb like praviti when the noun is the thing being made, Croatian uses the accusative:

• pravim juhu = I make soup

So:

• nominative: juha
• accusative: juhu

This is a very common feminine noun pattern.

Poriluka is genitive singular.

The preposition od usually takes the genitive, and here it means something like:

• made from
• of
• with ... as the main ingredient

So:

• poriluk = leek
• od poriluka = of leek / made from leek

In food names, this is very common:

• juha od rajčice = tomato soup
• sok od naranče = orange juice
• pire od krumpira = mashed potatoes

So juha od poriluka is simply the normal way to say leek soup.

Zato što means because.

It appears twice because the sentence is contrasting two reasons:

• not because it is the cheapest
• but because grandma always cooked it that way

So the repetition is very natural and helps make the contrast clear.

You could think of the structure like this:

• Ne X zato što A
• nego zato što B

Croatian also has other ways to say because, such as jer, but zato što fits especially well in this kind of contrastive sentence.

Because it agrees with an understood feminine noun, namely juha.

The adjective is describing the soup:

• juha is feminine singular
• therefore the adjective is also feminine singular: najjeftinija

So the idea is:

• jer je najjeftinija juha
• or more naturally, jer je najjeftinija

Croatian often leaves out a noun when it is obvious from context. English does this too sometimes:

• This one is the cheapest.

Here, the omitted thing is the soup.

Also, the form is built like this:

• jeftin = cheap
• jeftinija = cheaper
• najjeftinija = the cheapest

Here nego means but rather.

After a negated statement, Croatian often uses nego instead of ali when correcting or replacing one idea with another.

So:

• ne zato što A, nego zato što B
  = not because A, but because B

This is more precise than ali.

A useful rule of thumb:

• ali = general but
• nego = but rather / instead, especially after ne

So in this sentence, nego is exactly the right choice.

Because je is a clitic, and Croatian clitics usually go in the second position of the clause.

In the subordinate clause:

• što je baka uvijek tako kuhala

the auxiliary je comes very early, which is normal Croatian word order.

So this is standard:

• što je baka...

And this is not the normal standard order:

• što baka je...

The same thing happens very often in Croatian:

• Kad sam došao... = When I came...
• Jer je rekla... = Because she said...

Clitic placement is one of the trickier parts of Croatian for English speakers, because English does not have this same system.

This is the perfect tense:

• je kuhala = cooked / was cooking / used to cook

It is formed with:

• the auxiliary je
• the past participle kuhala

The participle kuhala is feminine singular because it agrees with baka, which is feminine:

• baka je kuhala = grandma cooked
• djed je kuhao = grandpa cooked

In this sentence, because of uvijek, the sense is probably habitual:

• baka uvijek tako kuhala = grandma always cooked it that way / used to cook it that way

So although Croatian uses the perfect tense, English often translates it with used to in this kind of context.

Because the two verbs focus on slightly different things.

• praviti juhu = to make soup
• kuhati = to cook

In everyday language, both can be used around food, but they are not identical.

Here:

• ne pravim juhu... focuses on the speaker’s act of preparing that soup
• baka uvijek tako kuhala refers to grandma’s habitual way of cooking it

So the sentence sounds natural. Croatian often varies verbs this way instead of repeating the exact same one.

Also, depending on region and style, some speakers might more often say:

• Ne kuham juhu od poriluka...

instead of Ne pravim juhu od poriluka...

But pravim is understandable and natural in many varieties.

Tako means like that, that way, or in that manner.

So:

• baka uvijek tako kuhala
  = grandma always cooked it that way

It refers to the particular method or tradition that the grandma used.

This word is important because the speaker is not just saying grandma cooked it. The point is:

• grandma cooked it in that way
• that is the tradition or style being followed

So the reason is not price, but family habit / tradition.

Yes. The pronoun it is not said explicitly, but it is understood.

Croatian often leaves out subjects and sometimes also leaves out nouns that are obvious from context. So:

• je najjeftinija = it is the cheapest

What it refers to is understood from the sentence, most likely the soup or that kind of soup.

This kind of omission is very normal in Croatian and often sounds more natural than repeating the noun unnecessarily.