Written for this prompt on Sherlock BBC Kink Meme: .?thread=6546343#t6546343

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Looking back now, John wasn't sure why he'd never thought of it. After all, it was chemistry, science. It was just that the very idea of Sherlock- that is to say, it was so ludicrous…

Who would have thought that Sherlock Holmes, the world's only consulting detective, would know how to bake?

Mrs. Hudson had mentioned in passing that the she wouldn't be going to the market on Monday, and that if they needed anything, it would have to wait until the following day. She was going out with friends for her birthday.

He had mentioned it, in turn, to Sherlock. John had just finished another blog entry, and Sherlock was in the kitchen, checking something in his microscope. The microwave was on, though what was in it, John preferred to ignore.

"You know, Mrs. Hudson's birthday is tomorrow."

"Is it? That's nice." Sherlock's voice sounded distant, preoccupied. John was pretty sure he could have said that England had just been invaded by fairies in tanks and he would have received the same response. He pressed on.

"I thought, for a change, we might do something for her. She's quite a nice woman. She puts up with your moods, and that's more than most could say."

"Hm."

John shook his head. "You do know that I can tell you're not really listening to me, right?"

"Of course."

Of course. Well, fine then. John would do something by himself. Maybe bake her a cake. He'd baked before, though it had been many years since. Then he'd just tag Sherlock's name on the note as well. Mrs. Hudson would be happy, he supposed. No need to make a huff over his flat-mate's apathy.

Just then the microwave semi-exploded and the flat filled with smoke and the reek of singed hair, and John's plans were put on hold for the evening.

It hadn't gone at all as he expected. John had thought it would be simple. It was just chocolate cake. It couldn't be that hard. But then the chocolate had burned on the stove, and he'd knocked the bowl with the flour off the counter trying to get it off. He'd thought he had milk in the fridge, but it had gone sour, and he hadn't noticed until it had already been mixed in with the other wet ingredients.

When Sherlock walked into the flat half an hour later, it was to find a thoroughly disgruntled and irritated John in a stained apron, absolutely covered in flour and cocoa powder.

The consulting detective hardly even blinked.

"If you're trying to make a cake, the flour's meant to go in the bowl, John, not your hair."

"Fuck off."

Sherlock raised an eyebrow, stepping forward and wiping a smudge of chocolate from John's chin with his thumb.

"Hm. Maybe later," he said, suggestively, putting the digit in his mouth and sucking.

John frowned.

"Right now, however, perhaps it would be better if I helped you with Mrs. Hudson's cake." He removed his jacket and began to unbutton and roll-up his sleeves.

"I thought you weren't really listening last night, and- hang on, what do you know about baking?" John rubbed at the chocolate smudge on his chin, making sure to get the rest of it off.

"John, when will you learn that I am essentially always listening to you, though it may seem otherwise at times?"

John crossed his arms, looking a bit sullen.

"As for baking. I'll have you know I happen to be a most excellent baker."

This seemed so incredibly unlikely to John that he snorted, a small cloud of white flour puffing about his nostrils.

"Yes, yes. Be as derisive as you want. You're the one covered in flour, and-" Sherlock suddenly sniffed at the air. "Did you try and melt chocolate directly on the stove?"

John had the good grace to look slightly abashed.

"Right, you sit." Sherlock pointed at the kitchen stool, tying a second apron around his waist. "It's clear that you lack a baker's touch. I'm assuming, from the copious amounts of both baking chocolate and cocoa powder that you were attempting to create something resembling a chocolate cake."

John mumbled to himself.

"Sorry, John, what was that? Didn't quite catch the last bit!" Sherlock looked positively gleeful. There was a glint in his eyes that John usually only saw when he was on a case.

And so John resolved to sit and let Sherlock take control of the situation, and as Sherlock began to move around the kitchen, pulling out pots (they had a double broiler?) and getting more eggs out of the fridge, John couldn't help but smile at something so simple giving the detective so much enjoyment.

The chocolate was set to melt, and Sherlock beat the eggs with a flair bordering on the dramatic. He was a whirlwind in the kitchen, sifting flour and sugar together, measuring out baking powder and salt, tempering the eggs with the chocolate, all done with a grace that John could never hope to possess. And without a recipe.

"Where did you learn to do this?" John finally asked, as Sherlock poured the batter into a prepared baking dish. He slid off his seat and came to stand next to his partner as the cake went in the oven.

Sherlock shrugged. "My mother has always loved to bake. She taught me, and the science of it always fascinated me. You must pay the utmost attention to detail, or everything falls to pieces."

John nodded. Yes. It did make sense, but still. So strange.

Sherlock turned around and John spotted a smudge of chocolate above his eyebrow.

Turnabout's fair play.

He smirked and rubbed it off with his thumb, but Sherlock's hand darted out and caught John's wrist. The detective's smile could only be described as devious, and then John's head was falling back as he groaned, his thumb surrounded by the moist warmth of Sherlock's mouth. Sherlock's tongue moved in languorous strokes around the digit, licking and sucking the chocolate clean. He hummed in what sounded like appreciation and the vibrations made John's skin break out in goose-bumps. When Sherlock scraped John's thumb with his teeth, he felt his legs begin to give way, and he leaned back against the counter, propping himself up with his other hand.

Sherlock let John's wrist go and pushed forward, hips grinding into the other man's, and John's hands shot out, gripping at the back of Sherlock's shirt for purchase. The detective's mouth was now sucking greedily at a spot just below John's ear, and he was trying desperately to keep a clear head.

Any hopes for that, however, disappeared when Sherlock left John's neck alone for just long enough to whisper, breath hot against his skin, "But my favorite part about baking, is what you can do with leftover batter."

Mrs. Hudson had had a lovely evening at the pub with her friends. Goodness! It had seemed like ages since she'd had a night out. The girls had even gotten together to buy her a nice set of gold earrings that she honestly didn't know when she would wear, but it was the thought that was important. The only thing missing had been a-

Mrs. Hudson stopped short in front of her door. There, on the door mat, was a small white box with writing on it-

Mrs. Hudson-

Happy Birthday!

From your boys upstairs.

It was signed with two chocolate smudged thumbprints.

And it was, perhaps, the most delicious cake she'd ever tasted.