The phrase "during my breakfast" is correct and usable in written English.
You can use this phrase any time you want to indicate something that was occurring while you were having breakfast. For example, "I read the newspaper during my breakfast this morning."
Why do I keep reading about murder and mayhem not only in parked cars, but at the breakfast table, during my son's gymnastics practice, waiting at the airport, and late at night after the house is asleep and I'm the only one with a light burning?
One morning when my daughter was two months old I leaned over to my husband during breakfast and with zero emotion said, "I feel like I want to be dead but don't worry, I know I need to take care of our baby so I won't do anything stupid.
I really like the girls that will rip my heart from my ribs and make my life miserable during breakfast the next day, and to be honest those types of ladies could care less about my "history".
Besides, I'd already had a brush with possible bodily harm that morning, during breakfast in my hotel.
My heart was racing during the breakfast shift as I waited for the news about my PhD.
DURING an otherwise routine breakfast, my husband suddenly looked over the top of Sports and said, "Have you seen my green shoes?" "I knew it," he said.
But it won't be leaked at my suggestion," Levin said, during a breakfast sponsored by the Christian Science Monitor.
One time I even watched the nominations at the campus center during breakfast live on my, wait for it, Sony Watchman.
The other day, my husband — who believes every holiday and even the observance of birthdays is a plot devised by greeting-card companies — mentioned during breakfast that it was my cousin's birthday.
For example, SI was estimated as SI(D) during dinner, SI(N1) during early night, SI(N2) during late night, and SI(B) during breakfast.
