Six fire engines and around 40 firefighters tackled a building fire on Curtain Road in Shoreditch.
Half of a basement kitchen and part of the ground floor of a building was damaged by fire. Ducting running from the kitchen to roof level was destroyed by fire.
A man left the building before firefighters arrived and was treated at the scene by London Ambulance Service crews for smoke inhalation. Another man was led to safety by firefighters from a third floor flat via an external staircase.
Road closures were in place at the junction of Curtain Road and Great Eastern Street while the incident was dealt with.
The Brigade was called at 1030 and the fire was under control by 1115. Crews from Shoreditch, Bethnal Green and surrounding fire stations attended the scene.
The fire is being treated as accidental and believed to have been caused by cooking left unattended.
A London Fire Brigade spokesperson said: "Fires are more likely to start in the kitchen than any other room.
"Cooking should never be left unattended on the hob or grill - if you have to leave the kitchen, turn off the heat.
"Chip pans and cooking with hot oil can be really dangerous and the risk increases when you start frying food more than once.
“All it can take is for you to become distracted for a few seconds and your cooking oil can quickly go up in flames.”
“This incident is a timely reminder to make sure you never leave cooking unattended. If you do have to leave the room or house, turn the heat off.”