"Merlin, what is wrong with me?" Snape asked as he entered the basement and warded the door. It wouldn't do for Harry to hear him talking to himself, especially not right now.
"How can I be having such thoughts about a former student? And Harry Potter no less. I must have lost my mind!"
Because he's an attractive young man, who is walking around practically naked in your kitchen; it's perfectly normal to think those thoughts about an attractive young man. He tried to rationalize with himself.
Severus continued to pace the length of the basement talking to himself, trying to rationalize the attraction he suddenly felt toward Harry, but his conscience seemed to be having fun teasing him and making him feel guilty.
Meanwhile Harry was upstairs pondering what the look on Severus' face meant as he had come up the stairs and found Harry in the kitchen poking around. "Must have been shocked to see me up, is all," Harry muttered. Harry forgot about Severus when he found pancake mix and blueberries in the refrigerator. Grabbing them both he went to the stove and began making pancakes.
After making a huge stack for himself, he made a couple of extra and tossed them on another plate for Severus. I am eating the man's food, at least I can save some for him, Harry thought, and sat the plate on the back of the stove to keep it warm.
Realizing he had no syrup, he started to dig in the cabinets again and found a large bottle behind what Harry could only guess were potions ingredients. As he carried it back to the table, he thought and stopped at the basement door, knocked and yelled, "Pancakes, Severus!" and went on to sit down.
Harry dived into his pancakes like a starved animal, and unknown to him Severus was standing below in the basement, wondering if he should go up and eat with the boy or not.
"I am rather hungry," he told himself, not entirely sure if he was lying or not. "What the hell?" he said, and headed up stairs.
When he got to the kitchen, Harry was sitting at his table halfway through what looked like a dozen pancakes piled on his plate, and didn't seem to have any intentions of stopping anytime soon.
Rather than sitting down to eat with Harry, Severus went to his bedroom and closed the door. After taking off his cloak, he stripped down, cast a couple of refreshing charms and redressed in clean clothes. No need to sit at the table smelling like jaguar's tongue or mashed bitterroot and ruining the boy's first real meal in days, he told himself.
Looking at himself in the mirror, satisfied that he didn't look the "Greasy old bat" that he had heard so many times in the halls at Hogwarts, he headed back to the kitchen and joined Harry for breakfast.