R/Hr: Because Harry Isn't Up To It
Some of my friends have already been amusing themselves with this fic, and now I see why. It's practically the silliest thing I've read in HP fandom, which takes some doing. Regency H/Hr.

“I – I’m sorry to disturb you,” she said, stepping tentatively into the room, “but I’m a little…er…perplexed.”

The bedclothes rustled as Harry sat up. “Well, come here and tell me what is troubling you.”

Hermione padded barefoot over to his bed and sat hesitantly. She was grateful now for the darkness, for it meant Harry would not be able to see her blush as she attempted to explain herself.

“As I said, I’m a bit perplexed because…well, I’ve been told that upon one’s wedding night, it is…er…customary, to consummate the marriage, and…well, we don’t appear to be doing that.”

Harry’s reaction was a rather audible intake of breath.

“I – I did not think you would…want to…er…consummate,” Harry said. “Until such time as you wanted to have children, of course. Presuming you want to have children at all.”

“I did not think I had a choice,” Hermione replied truthfully.

“Well…you certainly ought to. As I’m sure you’ve heard, it is…quite painful for a lady, the first time, and I do not wish to inflict that upon you until it is necessary.”

This is Chapter Two. By Chapter Six, Hermione and Harry have advanced to sharing a bed. By Chapter Eleven, they consummate the marriage.