Learn Turkish: Simit ve çay ile kahvaltı ettik. - We had breakfast with simit and tea.

Both kahvaltı etmek and kahvaltı yapmak mean "to have breakfast" and are completely interchangeable in everyday Turkish. You will hear native speakers use both frequently.

How is the word ettik formed?

It comes from the helper verb etmek (to do/make). We take the root et-, add the past tense suffix -di, and the "we" ending -k. Because t is a hard consonant, the d in -di changes to a t to match it, giving us ettik (we did/made).

Could I attach ile directly to the word çay instead of keeping it separate?

Yes! The word ile (with) can be written as a separate word or attached as a suffix (-la or -le). You could easily say simit ve çayla kahvaltı ettik and it would mean exactly the same thing. Both forms are perfectly natural.

Why doesn't the sentence say bir simit (a simit)?

In Turkish, when you talk about consuming something in a general sense—like having tea or simit for breakfast—you usually drop the word bir (a/one). You are talking about the category of food you ate, rather than pointing out that you ate exactly one simit.