Learn Hardcore Icelandic: Hún steikir fisk á pönnu og hrærir í sósu í litlum potti. - She fries fish in a pan and stirs the sauce in a small pot.

Each clause follows: Subject – Verb – (Object / Adverbials)
The subject Hún is not repeated before hrærir, but it’s understood to be the same subject in both clauses, which is normal in Icelandic (as in English: She fries fish and stirs the sauce).

Why is it steikir and hrærir, not something like steikjar or hræra?

Steikir and hrærir are the 3rd person singular present tense forms of the verbs:

að steikja – to fry
- ég steiki
- þú steikir
- hún / hann / það steikir
að hræra – to stir
- ég hræri
- þú hrærir
- hún / hann / það hrærir

So Hún steikir and Hún hrærir both mean “She fries / she stirs”.
The infinitive forms steikja, hræra change their endings in the present tense, as shown above.

Why is the word fisk (without -ur) used here?

The base (nominative singular) form of the noun is:

fiskur – fish (a fish)

In the sentence, fisk is the direct object of the verb steikir, so it appears in the accusative singular:

Nominative: fiskur (subject)
Accusative: fisk (direct object)

Icelandic changes noun endings according to case; here we need accusative because something is being acted upon (she fries what? → fish).

Why does á pönnu use á with the dative case, and what does pönnu mean exactly?

The preposition á can govern either accusative or dative, depending on the meaning:

á + accusative = motion onto something
á + dative = location on / in something (no movement)

In á pönnu there is no movement; the fish is already being fried in / on the pan, so á takes the dative.

The noun:

Nominative: panna – (frying) pan (feminine)
Dative singular: pönnu

The vowel change a → ö is a regular type of umlaut in Icelandic declension.

So á pönnu literally means “on/in (a) pan” and is best translated here as “in a pan”.

Why is there no word for “a” or “the” before fisk, pönnu, sósu, and litlum potti?

Icelandic does not use separate words like English “a” and “the”.
Instead, it uses:

no article = usually indefinite (a fish, a pan)
a definite suffix attached to the noun = the (the fish, the pan)

Here we have indefinite nouns:

fisk – (a) fish
á pönnu – in a pan
í sósu – in (a) sauce / in sauce
í litlum potti – in a small pot

If you wanted to say “the” explicitly:

fiskurinn – the fish
á pönnunni – on the pan / in the pan
í sósunni – in the sauce
í litla pottinum – in the small pot

So the sentence is talking about some fish, some sauce, a small pot in general, not specific known ones.

Why does hrærir take í sósu instead of just sósu?

The verb að hræra (to stir) is often used as a prepositional verb with í + dative when you mean “to stir something that is already in a container”:

hræra í grautnum – stir the porridge
hræra í pottinum – stir the pot
hræra í sósu – stir the sauce

Grammatically, í sósu is functioning like the object of the verb, but it appears as a prepositional phrase with í + dative:

Nominative: sósa
Dative singular: sósu → after í

You can also find hræra sósu / sósuna in Icelandic, but hræra í sósu is a very natural, everyday way to say “stir the sauce.”

Why is í repeated twice: í sósu í litlum potti? Could you drop one of them?

The two í phrases express two different relationships:

í sósu – what is being stirred (the sauce)
í litlum potti – where the sauce is (in a small pot)

So the structure is:
hrærir [í sósu] [í litlum potti]
= stirs the sauce in a small pot.

You cannot simply drop one í, because that would change or obscure the meaning:

hrærir sósu í litlum potti – would sound more like “stirs sauce into a small pot” (motion into)
hrærir í sósu litlum potti – ungrammatical / very odd

Each í is required for clarity: first to mark what she stirs, second to mark the location.

What cases and genders are used in í litlum potti, and why?

Í litlum potti consists of:

í – preposition
litlum – adjective: “small”
potti – noun: “pot”

The noun:

Nominative: pottur (masculine) – a pot
Dative singular: potti

The preposition í (like á) can take either accusative or dative:

í + accusative – motion into something
í + dative – location in something

Here we have a location (the sauce is already in a small pot), so í takes the dative:

potti – masculine dative singular
litlum – masculine dative singular of lítill (small), agreeing with potti in gender, case, and number

So í litlum potti = “in a small pot” (static location, hence dative).

How would the sentence change if I wanted to say “the fish”, “the sauce”, and “the small pot”?

You would add definite suffixes to the nouns and adjust the adjective accordingly:

fisk → fiskinn (accusative singular definite: the fish)
í sósu → í sósunni (dative singular definite: in the sauce)
í litlum potti → í litla pottinum (dative singular definite with adjective)

Full sentence:

Hún steikir fiskinn á pönnunni og hrærir í sósunni í litla pottinum.
= She fries the fish in the pan and stirs the sauce in the small pot.

Could I instead say Hún er að steikja fisk og hræra í sósu? How is that different?

Yes, that is also correct Icelandic, and it’s a very natural alternative.

Hún steikir fisk… – simple present, can describe a present action or a general habit.
Hún er að steikja fisk… – literally “She is to fry fish,” functionally a present progressive, similar to English “She is frying fish.”

So:

Hún steikir fisk á pönnu og hrærir í sósu í litlum potti.
Hún er að steikja fisk á pönnu og er að hræra í sósu í litlum potti. (or just og hrærir í sósu…)

Both can refer to what she is doing right now; er að + infinitive just makes the “ongoing action” feel more explicit, like English -ing.

Why isn’t Hún repeated before hrærir?

In Icelandic, as in English, when two verbs share the same subject in a coordinated structure with og (and), you usually do not repeat the subject:

Hún steikir fisk og hrærir í sósu.
= She fries fish and (she) stirs the sauce.

The subject Hún automatically applies to both verbs: steikir and hrærir.
Repeating it (Hún steikir fisk á pönnu og hún hrærir í sósu…) is grammatically possible but sounds heavier and is normally only done for emphasis or contrast.

How do you pronounce some of the “strange” letters, like ú, æ, and ö in this sentence?

Very roughly, using English approximations:

Hún – ú is a long [uː], like oo in food (but tenser and longer).
steikir – ei is pronounced like [ei], close to the vowel in English day.
fisk – as spelled, similar to English fisk (short i as in sit).
pönnu – ö is like German ö (IPA [œ]), somewhat between English e in her and u in burn, but with rounded lips.
sósu – ó is a long [ou], like English go, and ú again like oo in food.
potti – tt is a double consonant; the vowel before it is short (o is quite like the o in hot for many speakers).

Precise Icelandic pronunciation is more systematic than English, but these hints are enough to get you close for this sentence.