Sherlock emerged from the kitchen bearing a plate, upon which sat a round object, roughly five and a half inches in diameter. It was dark brown, lumpy and uneven, and resembled nothing so much as a new kind of sponge from the deep ocean.
He beamed, "I made you something!"
John looked up, "What is it?"
"It's a cake!"
"For a case?"
"No, it's for you," he smiled.
"Is it poisonous?"
Sherlock looked puzzled and more than a little crushed. "No, it's a cake."
"Is it full of metal?"
"Of course. It's a cake."
"What?"
"Most elements are classified as metals."
"Is it radioactive?"
"Of course not. I don't have access to radioactive materials since my source dried up. It's just a cake."
"Where did it come from?"
Sherlock was looking distinctly unhappy by this time, "I made it. I told you that."
"Is it an experiment involving digestion, because that last one really did not—"
"Oh, for God's sake, JOHN, it's a cake. Just a cake. I baked you a cake, because that's what you do for someone you love."
To prove his point, Sherlock rucked up John's t-shirt and ground the whole sticky goodness onto John's tummy. He bent down, smooshed his face into it and took several large bites. "It is, or was, just a bloody cake!"