Min søster tilsætter kanel og vanilje, før hun blander gæren i mælken.

Because søster is a common gender noun in Danish, and common gender nouns take min for my.

• min søster = my sister
• mit hus = my house

So the possessive changes according to the noun’s gender:

• min
  • common gender
• mit
  • neuter
• mine
  • plural

Tilsætter means adds or adds in, usually when you put an ingredient into something.

Blander means mixes.

So there is a useful distinction:

• tilsætte kanel og vanilje = to add cinnamon and vanilla
• blande gæren i mælken = to mix the yeast into the milk

In cooking Danish, tilsætte is very common for adding ingredients.

Danish often uses the present tense for:

• habitual actions
• instructions
• describing a process
• telling what someone usually does

So this can mean something like:

• she usually adds cinnamon and vanilla before mixing the yeast into the milk
• or it can describe a step in a recipe-like way

That is very natural in Danish, just as in English you might say First she adds..., then she mixes...

Because før hun blander gæren i mælken is a subordinate clause.

In standard Danish, a subordinate clause is often separated by a comma:

• Min søster tilsætter kanel og vanilje, før hun blander gæren i mælken.

Here:

• main clause: Min søster tilsætter kanel og vanilje
• subordinate clause: før hun blander gæren i mælken

The conjunction før means before and introduces the subordinate clause.

Because Danish normally requires an explicit subject in a clause.

So after før, you need:

• hun blander

You cannot usually leave out the subject the way some languages can. Danish works more like English here:

• before she mixes... not
• before mixes...

Gæren is the definite form of gær.

• gær = yeast
• gæren = the yeast

Danish often uses the definite form where English might or might not use the, especially when talking about a specific ingredient already understood in the situation.

In a baking context, gæren sounds natural because it refers to the yeast being used in the recipe.

Because blande noget i noget means mix something into something.

So:

• blande gæren i mælken = mix the yeast into the milk

If you used med, that would suggest with, which is a different relationship:

• blande noget med noget = mix something with something

Both patterns exist in Danish, but here i mælken focuses on the yeast going into the milk.

Yes, after før introducing a subordinate clause, Danish uses subordinate clause word order.

Here that gives:

• før hun blander gæren i mælken

The subject hun comes before the verb blander.

This is different from main clause word order, where Danish often has verb-second structure. For example:

• Min søster tilsætter ...
• Nu tilsætter min søster ...

But in the subordinate clause after før, you do not do that inversion.

That is just the normal way to join two nouns in Danish, just like in English:

• kanel og vanilje = cinnamon and vanilla

If there were more items, Danish usually works similarly:

• kanel, vanilje og sukker

So nothing unusual is happening there.

A few pronunciation points are especially useful for English speakers:

• søster: the ø is a front rounded vowel, something like saying eh while rounding your lips
• før: the ø sound appears again
• gæren: æ is more open, a bit like the vowel in English cat, but not exactly
• mælken: again the æ sound

Also remember:

• final -er in Danish is often reduced and not pronounced as clearly as English er
• d is often soft or silent in many words, though not relevant in all of these
• g in gæren is pronounced, unlike some places where Danish consonants weaken

If you are learning pronunciation, the main challenge here is really the vowels ø and æ.

Yes, if you move another element to the front, Danish changes the word order in the main clause because of the verb-second rule.

For example:

• Før hun blander gæren i mælken, tilsætter min søster kanel og vanilje.

Now the subordinate clause comes first, so in the main clause the verb tilsætter comes before the subject min søster.

That is very important in Danish:

• if something else comes first in a main clause, the finite verb usually comes second

By itself, vanilje usually just means vanilla in a general sense.

In real cooking context, Danish can be more specific:

• vaniljesukker = vanilla sugar
• vaniljeekstrakt = vanilla extract
• vaniljestang = vanilla pod / vanilla bean

So vanilje here is general unless the wider context tells you exactly which form is meant.

Yes, in a baking context it often can.

Literally it means mix the yeast into the milk, but depending on context it may imply:

• stirring it in
• combining it
• dissolving fresh yeast into the milk

Danish often leaves that practical detail to context, especially in recipe-style language.