I conduct biographical research. I'm using two techniques: narrative interview (main technique) and biographical essay. I need a literature about biographical essay as technique?
I'm not familiar with research on the topic of biographical essays as a research technique. On the other hand, there is a wonderful book by Howard Gruber who analyzed Darwin's journals as a way to understand Darwin's developing understandings of evolution. I think that Gruber wrote about analyzing Darwin's notes as a technique to conceptualize development.
Hope this is in the direction of what you are looking for.
Stanley Cavell has been a champion in doing philosophy through autobiography. His most recent book, Little Did I Know (wonderfully reviewed, eg. by Emily Budick) is his autobiography but even previously, e.g. in A Pitch of Philosophy, he investigates philsophical problems through his (and our) everyday life, the ordinary. Cavell is an extra-ordinary, very profound thinker, one of the greatest of our times, I recommend him highly! :)
Dear Aleksandra, it is not really clear what exactly do you mean by biographical essay as a research technique in biographical research. Could you explain it a bit?
I would recommend as an introduction the online article on autobiography in the "living handbook of narratology", written by Helga Schwalm, see the link below. There you will find a lot of further primary and secondary sources, be they of theoretical nature such as the aforementioned Gerard Genette ("Fiction and Diction") or Philippe Lejeune ("On Autobiography"), or be they studies on the history of the form.