A/N: This is an AU, because a) I like AUs and b) the story I wanted to write wouldn't have been able to happen if it weren't. Also, this is doubly an AU because there is no Dark Lord and Petunia Evans will not marry Vernon Dursley.
A/N2: This is probably the only Lilybashing fic in existence. I haven't checked, but I've been reading fanfiction since early 2000 and I've never seen any.
A/N3: I will put new chapters up as soon as they're written, so don't nag. Also, this will not rise above PG-13 or T, as I cannot bring myself to write hetsmut.
The Slytherin's Guide to Dating
Step Three: Ask Your Parents' Permission
Severus entered the flat over the apothecary shop with a vaguely foolish look on his face. He was clutching a piece of paper in one hand and looking at it as if it were the greatest treasure he'd ever seen. His mother, who was doing the accounts, heard the door close behind him.
"Severus, where have you been? Your father's been looking for you."
"Mother, I've just met the most wonderful girl in the world."
"And what's so wonderful about her, may I ask?" His mother was skeptical.
"She's intelligent. She has a sarcastic sense of humor. She's well read. She's the most beautiful girl in the world and she thinks I'm handsome. She's absolutely perfect."
His mother twisted in her seat and took in the expression on his face in astonishment. "Severus, you've fallen in love!"
Severus blushed. "And if I have, what of it?"
"Then it's wonderful! Your father and I have been wondering when you'd find a nice girl and settle down. Both of your brothers had been betrothed a year or more at your age. Now, have a seat and tell me what she's like, and I don't mean what you told me before. What's her name? What does she look like? How old is she? Where is she from?"
"She's tall and slender and her hair is dishwater blonde. Her eyes are intensely green and she moves like a dancer. She's just turned seventeen and she's from Surrey. Her name is Petunia Evans and she's Lily Evans' younger sister. She's also a Muggle and I really don't care."
"Severus, you're the third son. It wouldn't matter to us if you married a hippogriff just so long as you loved it." Madam Snape was dismissive. "Do you intend to court her?"
"Would you let me?" Severus was mildly astonished.
"I would, and your father can be persuaded. Do you intend to see her again soon?" She had become all business.
"I'm going to take her to lunch tomorrow." Severus admitted sheepishly.
"And you didn't think to ask us first? Oh well, no matter. You'll need to bring flowers if you're going to do this formally. Hmmm... Seven light pink roses I think. Seven for infatuation and light pink for admiration. And a copy of the Language of Flowers. I don't think Muggles know it." She said thoughtfully.
"Yes, Mother. What should I wear? I haven't got any nice Muggle clothing." Severus looked suddenly worried.
"Well, where are you taking her?"
"I was going to take her to Chef Chang's for Chinese food, but I don't know if it's appropriate for a formal courtship." He imbued the last two words with reverence.
"Of course it is. I'll get your father to loan you his Nehru jacket, then you'll be set. If there's not anything else, I need to finish writing these bills out." She turned back to work, and Severus wandered blissfully into his room and locked the door.
Once he was guaranteed privacy, Severus turned to his mirror and looked at his hair consideringly. He tried pulling it back into a ponytail and concluded it made him look awful. Then he tried gathering it at the nape of his neck. There, that was better. It looked somewhat sophisticated, and was easy to do, so he decided to wear his hair like that for his date with Petunia.
Then he went over to his closet and looked at his pitifully small collection of Muggle clothes. Two more pairs of black jeans, three more plain black t-shirts and a variety of t-shirts he'd gotten at concerts. He briefly considered wearing a Led Zeppelin t-shirt for his date but decided against it. He would just have to borrow a shirt from his father as well.
Having done what he could in terms of his outfit, Severus went out, to the little flower shop across the street. When he brought the roses he'd selected to the counter, the shopgirl giggled, and asked him if he wanted them in a vase, to which he readily agreed. The cost of the book was surprisingly high, but he paid it gladly. It was, after all, for Petunia.