Hun spiser bedst, når grøden ikke er for varm, og når mosen er helt blød.

Because bedst is the superlative adverb of godt/god.

Here it modifies the verb spiser (eats), so Danish uses the adverb form:

• god = good
• godt = well / good
• bedre = better
• bedst = best

So:

• Hun spiser godt = She eats well
• Hun spiser bedst = She eats best

In English, best can also work this way, so the idea is similar.

Here når means when.

It introduces a clause that gives the situation in which something is true:

• Hun spiser bedst, når ... = She eats best when ...

In many contexts, når can mean when/whenever for repeated or general situations. In this sentence, it sounds like a general pattern: she eats best under these conditions.

It creates a neat parallel structure:

• når grøden ikke er for varm
• og når mosen er helt blød

This makes it clear that there are two separate conditions.

You could think of it as:

• She eats best when the porridge is not too hot, and when the mash is completely soft.

In Danish, repeating the conjunction is very natural here. It helps the sentence sound balanced and clear.

Because this is a subordinate clause introduced by når.

In Danish subordinate clauses, words like ikke often come before the finite verb:

• når grøden ikke er for varm

Compare that with a main clause:

• Grøden er ikke for varm.

So the contrast is:

• Main clause: subject + verb + ikke
  
  • Grøden er ikke for varm
• Subordinate clause: subject + ikke + verb
  
  • når grøden ikke er for varm

This is a very important Danish word-order pattern.

No. Here for means too, not the English preposition for.

So:

• for varm = too hot / too warm
• for kold = too cold
• for stor = too big

This is a very common Danish pattern: for + adjective = too + adjective.

Because they are in the definite singular form: the porridge, the mash.

In Danish, the definite article is usually attached to the noun as an ending:

• grød = porridge

• grøden = the porridge

• mos = mash / purée
• mosen = the mash

Both of these nouns are common gender nouns, so the usual definite singular ending is -en.

They are similar but not identical.

• grød usually means porridge or something cereal-based and spoonable
• mos usually means mash or purée, something mashed until soft

So the sentence is talking about two different kinds of soft food textures. A learner may notice that both are soft foods, but Danish still treats them as different nouns with different typical uses.

Because blød agrees with mosen, which is singular common gender.

After er, Danish adjectives still agree with the noun:

• mosen er blød = the mash is soft
  (mosen is common gender singular, so blød)

Compare:

• et æble er blødt = an apple is soft
  (et-word / neuter singular, so blødt)

• æblerne er bløde = the apples are soft
  (plural, so bløde)

So in this sentence, blød is the correct form.

Helt here means completely, entirely, or sometimes really.

So:

• helt blød = completely soft

It strengthens the adjective blød. Danish often uses helt this way:

• helt rigtig = completely right
• helt færdig = completely finished
• helt blød = completely soft

Because Danish normally uses a comma to mark the beginning of a subordinate clause.

So:

• Hun spiser bedst, når grøden ikke er for varm ...

That comma helps show that når grøden ikke er for varm is not a new main clause, but a clause depending on the first one.

Comma rules in Danish are often stricter and more visible than what English learners may expect.

Literally it is eats best, but in context it often means something like:

• she eats most successfully
• she eats most comfortably
• she eats most willingly

So it can describe not just skill, but the conditions under which eating goes best for her.

That kind of broader meaning is very natural in Danish.

The ø sound does not exist in standard English, so it can be tricky.

A rough guide:

• ø is somewhat similar to the vowel in French deux or German schön
• It is not like English oo or oh

So grøden is roughly something like GRUH-dən / GRER-dən, but no English spelling captures it exactly.

Also, the d in words like grøden is often a soft Danish d, not a hard English d. That makes the word sound smoother than English speakers usually expect.

Yes, varm can mean both warm and hot, depending on context.

In this sentence:

• ikke er for varm most naturally means is not too hot

That is because we are talking about food and eating. If food is for varm, it is too hot to eat comfortably.

So the exact English translation depends on context, but the Danish word is the normal one here.