Djeca uvijek traže još jednu porciju juhe kad je baka kuha.

Because the subject djeca means children, so the verb has to be plural.

• dijete traži = the child asks / is asking
• djeca traže = the children ask / are asking

So traže is the 3rd person plural present form of tražiti.

Because djeca is an irregular plural of dijete.

• dijete = child
• djeca = children

This is something learners usually just have to memorize. Croatian has a few common nouns with irregular plural forms, and dijete → djeca is one of the most important ones.

Uvijek means always.

Its position is fairly flexible, but Djeca uvijek traže... is a very natural, neutral word order. Croatian often places adverbs like uvijek before the main verb.

You may see other orders in different contexts, but this one sounds straightforward and normal.

Here još jednu means one more or another.

• još = more / still / additional
• jednu = one in a form that matches porciju

So još jednu porciju is not just one portion, but one more portion.

Because this is the direct object of the verb traže, so Croatian uses the accusative case.

The base form is:

• jedna porcija = nominative

But after traže it becomes:

• jednu porciju = accusative

Also, porcija is a feminine noun, so jednu has to match it.

Because after a noun like porcija (portion), Croatian usually puts the thing being portioned in the genitive.

So:

• porcija juhe = a portion of soup
• čaša vode = a glass of water
• kilo jabuka = a kilo of apples

Here:

• porciju = accusative, because it is the direct object
• juhe = genitive, because it depends on porcija

If soup itself were the direct object, then you would say juhu, for example:

• Baka kuha juhu. = Grandma is cooking soup.

Here je is a short object pronoun meaning it, referring back to the soup.

So the last part literally works like:

• kad je baka kuha = when grandma cooks it

It is not the verb is here.

You could also hear ju instead of je in this kind of sentence, especially to make the meaning clearer.

Because je is a clitic: a short, unstressed word that usually goes near the beginning of the clause.

After kad, Croatian normally places clitics very early, so:

• kad je baka kuha sounds natural

A word order like kad baka je kuha sounds wrong in standard Croatian.

This early placement of short pronouns is a very common Croatian pattern.

Because the sentence describes a habitual or repeated action.

It means something like: whenever grandma cooks it, the children always ask for more. Croatian uses the present tense very naturally for this kind of general truth or repeated situation.

If you were talking about one finished event in the past, you would use past-tense forms instead.

Yes. Kad and kada both mean when.

In many situations they are interchangeable:

• kad je baka kuha
• kada je baka kuha

Very broadly:

• kad is a bit more common in everyday speech
• kada can sound a bit more formal or a bit more explicit

But both are correct here.

Because Croatian does not have articles like English the and a/an.

So nouns such as baka, porcija, and juha appear without articles, and the exact meaning is understood from context.

For example:

• baka can mean grandma, the grandma, or simply grandmother, depending on context
• još jednu porciju already gives the idea of one more portion, so no article is needed