Donna found him in the main kitchen on the ship. Honestly, what sort of a man has eighteen kitchens on his spaceship and only uses just one? However, the room was a mess. The counter was covered in miscellany, the sink was filled with unwashed dishes that looked like they'd been there weeks, and a cast iron pan had something burning in it that Donna doubted would ever be edible again. The Doctor looked up sheepishly at her from his mess. He was wearing nothing but a tartan dressing gown and bunny slippers.
"What in the name of sanity is going on in here?" Donna asked. She was too tired to shriek out the words like she normally would.
The Doctor coughed. "I was hungry. I'm making something to eat."
"Burning something, more like. Or is that what spacemen eat? Because I'm pretty sure they have those freeze-dried whatsits or something," Donna contemplated this, then said, "or is this why you insist we always land at some space-diner thingy instead of just using one of the various kitchens?"
The Doctor shrugged. He turned off the heat of the stove, scraping the burned mess into the trash. "You're right, I guess. I do have a nasty habit of burning things."
"You just don't want to admit you're a terrible chef, don't you?" Donna asked. The Doctor gave her an indignant look, then stacked the pan in the sink on top of the dish mountain.
After some arguing on the point of basic hygiene versus the Doctor taking care of his ship however he saw fit, Donna eventually won and made him clean up. She even helped organize the spice rack. Then, she made some Darjeeling, refusing the Doctor's help, and fixed them both plates of beans on toast.
"Show off," the Doctor grumbled through bites of Donna's culinary prowess.
"You're just jealous, spaceman. And don't talk with your mouth full." she said with her mouth full.
From then on, Donna resolved to teach the Doctor basic culinary skills so that when she was away, he wouldn't starve to death. Either way, she knew that despite being able to brag about all his Time-Lordy finesse, he would never be as good a chef as her. At least she had something to show off with, for once.