Min mor bruger et piskeris, når hun laver en let dej til pandekager.

Min mor means my mother.

• min = my
• mor = mother / mum

A few useful notes:

• mor is the normal everyday word, much like mum/mom in English.
• moder also means mother, but it sounds more formal or old-fashioned in many contexts.
• mors is the possessive form, meaning mother’s, so it would not fit here.

So Min mor bruger ... simply means My mother uses ...

Because piskeris is a neuter noun in Danish.

Danish nouns have two grammatical genders:

• common gender → takes en
• neuter gender → takes et

So:

• en bil = a car
• et hus = a house
• et piskeris = a whisk

There is no special logic you can always rely on; noun gender usually has to be learned with the noun.

Piskeris means whisk.

It is the kitchen tool used for beating or mixing things like eggs, cream, or batter.

So:

• et piskeris = a whisk
• bruger et piskeris = uses a whisk

Bruger is the present tense form of bruge.

• at bruge = to use
• bruger = use / uses

In Danish, the present tense often ends in -r:

• jeg bruger = I use
• hun bruger = she uses

So Min mor bruger et piskeris means My mother uses a whisk.

Når usually means when in the sense of:

• something that happens regularly or habitually
• something expected in the future

Here it works well because the sentence describes a typical situation:

• Min mor bruger et piskeris, når hun laver ...
• My mother uses a whisk when she makes ...

This suggests a repeated action, not one single past event.

These are easy to mix up.

• når = when, for repeated situations or future situations
• da = when, for one specific event in the past
• hvis = if

Examples:

• Når hun laver pandekager, bruger hun et piskeris.
  When she makes pancakes, she uses a whisk.
  repeated/habitual

• Da hun lavede pandekager i går, brugte hun et piskeris.
  When she made pancakes yesterday, she used a whisk.
  one specific past time

• Hvis hun laver pandekager, bruger hun et piskeris.
  If she makes pancakes, she uses a whisk.

So når is the right choice here.

Because når hun laver en let dej til pandekager is a subordinate clause, and Danish word order changes in subordinate clauses.

In a main clause, Danish often follows verb-second word order:

• Hun laver en let dej.
• literally: She makes a light batter.

But after a subordinating word like når, the subject usually comes before the verb:

• når hun laver ...
• not når laver hun ...

So this is standard Danish subordinate clause word order.

Because dej is a common-gender noun, so it takes en:

• en dej = a dough / batter

And the adjective appears as let here because that is the correct form before a singular indefinite common-gender noun:

• en let dej = a light batter

Compare:

• et let måltid = a light meal
  here måltid is neuter, so you also see let
• den lette dej = the light batter
  definite form changes to lette

So in this sentence, en let dej is grammatically correct.

Yes. Dej is broader than English dough.

In Danish, dej can refer to mixtures that English might call:

• dough
• batter

So for pancakes, dej often means batter, even though the direct English cognate might make you think only of dough.

You may also see:

• pandekagedej = pancake batter

In this sentence, en let dej til pandekager is best understood as a light batter for pancakes.

Here til means for / intended for / used for.

So:

• dej til pandekager = batter for pancakes
• literally, something like batter for making pancakes

Danish often uses til where English uses for to show purpose or intended use.

Examples:

• en kop til kaffe = a cup for coffee
• en pose til brød = a bag for bread
• dej til pandekager = batter for pancakes

So til is the natural preposition here.

Because pandekager is being used in a general sense.

• til pandekager = for pancakes
• not for the pancakes or for some pancakes specifically

If you wanted to refer to specific pancakes, you might phrase things differently depending on the context. But here the meaning is general: this is batter intended for making pancakes.

So the bare plural pandekager is completely natural.

Because når hun laver en let dej til pandekager is a subordinate clause, and Danish spelling rules normally place a comma before such clauses.

So the structure is:

• main clause: Min mor bruger et piskeris
• subordinate clause: når hun laver en let dej til pandekager

That is why you get:

• Min mor bruger et piskeris, når hun laver en let dej til pandekager.

The sentence is in the present tense:

• bruger = uses
• laver = makes

Danish, like English, often uses the present tense for:

• habitual actions
• general truths
• repeated situations

So this sentence means something like:

• My mother uses a whisk when she makes a light pancake batter
• or more naturally, My mother uses a whisk when she makes a light batter for pancakes

It describes what she generally does, not necessarily what she is doing right now.