Learn Dutch: Ik heb het mengsel ingekookt. - I have boiled down the mixture.

We use hebben because the verb inkoken (to boil down) is used transitively here. This means there is a direct object receiving the action: you (ik) are actively reducing something else (het mengsel). If the mixture had boiled down by itself (an intransitive change of state), you would use zijn: Het mengsel is ingekookt.

How is the past participle ingekookt formed?

Inkoken is a separable verb made up of in + koken. When forming the past participle of a separable verb, the ge- prefix is placed between the separable prefix and the main verb. Since the past participle of koken is gekookt, the full word becomes ingekookt.

Where should I put ingekookt if I add more information, like 'in a pan'?

The past participle ingekookt must remain at the very end of the clause. Any extra details go before it. For example: Ik heb het mengsel in een pan ingekookt. This creates a 'verb bracket' where the auxiliary verb (heb) and the past participle enclose the rest of the sentence.

How would I use ingekookt as an adjective to say 'the boiled-down mixture'?