U umak od gljiva dodajem vrhnje i malo peršina.

Because with u, Croatian uses:

• accusative for movement/direction into
• locative for location in

Here, dodajem suggests putting something into the sauce, so u umak is correct.

• u umak = into the sauce
• u umaku = in the sauce

So the sentence is treating the sauce as the destination of what you are adding.

The preposition od usually takes the genitive case.

So:

• gljive = mushrooms
• od gljiva = of mushrooms / made from mushrooms

In this sentence, umak od gljiva means mushroom sauce, literally sauce of mushrooms or sauce made from mushrooms.

It only looks singular to an English speaker. Here gljiva is actually the genitive plural form of gljiva.

The noun declines like this:

• nominative singular: gljiva = mushroom
• nominative plural: gljive = mushrooms
• genitive plural: gljiva

So after od, you need the genitive, and the correct form is gljiva.

After quantity words like malo (a little, a bit of), Croatian usually uses the genitive.

So:

• peršin = parsley
• malo peršina = a little parsley

This is very common:

• malo vode = a little water
• malo šećera = a little sugar
• puno ljudi = a lot of people

So malo peršina follows a very normal Croatian pattern.

Dodajem is the 1st person singular present tense of the imperfective verb dodavati / dodati.

Here it means:

• I add
• I am adding
• I usually add

Depending on context, Croatian present tense can cover several English possibilities.

Also, Croatian often leaves out the subject pronoun, so there is no need to say ja. The ending -em already tells you the subject is I.

Because Croatian verb endings usually show who the subject is.

• dodajem = I add
• dodaješ = you add
• dodaje = he/she/it adds

So ja is usually omitted unless you want emphasis or contrast.

For example:

• Dodajem vrhnje. = I’m adding cream.
• Ja dodajem vrhnje, a ti peršin. = I add the cream, and you the parsley.

Croatian has no articles like English a/an/the.

So umak, gljive, vrhnje, and peršin appear without articles. Whether something is a sauce, the sauce, some cream, or the parsley is understood from context.

That is why umak od gljiva can mean:

• a mushroom sauce
• the mushroom sauce

depending on the situation.

Yes. Croatian word order is more flexible than English because case endings show grammatical relationships.

The given sentence is natural:

• U umak od gljiva dodajem vrhnje i malo peršina.

But other orders are possible, for example:

• Dodajem vrhnje i malo peršina u umak od gljiva.
• Vrhnje i malo peršina dodajem u umak od gljiva.

These all mean roughly the same thing, but the emphasis changes. The original version puts the destination u umak od gljiva first, which can sound very natural in instructions or cooking descriptions.

In everyday Croatian, vrhnje often refers to cream, but in cooking it can mean different kinds depending on context, especially:

• cream
• sour cream
• sometimes cooking cream

If you want to be more specific, Croatian often says:

• kiselo vrhnje = sour cream
• slatko vrhnje = sweet cream / whipping cream
• vrhnje za kuhanje = cooking cream

So vrhnje by itself is a general word, and the exact type may depend on the recipe or context.

Because both are direct objects of dodajem, but they behave slightly differently:

• vrhnje is a mass noun and here it appears in its normal object form
• malo peršina is a quantity expression, and peršina is genitive because it follows malo

So in:

• dodajem vrhnje i malo peršina

you are adding two things:

1. vrhnje
2. malo peršina

Even though they do not look parallel at first, the structure is perfectly normal in Croatian.