Mine assured me he could never eat mushrooms, because even if there was only a tiny bit, he could taste it and it would ruin a meal.
So I diced a whole punnet very very finely. Like.. maybe 1mm cubes. TINY. I figured if he saw them, I'd say it was garlic. Anyway, it was in a lasagne. He never knew. lol. I haven't told him though cos he'll crack it... but I know he's obviously full of crap.
He also hates "homebrand," stuff, but I serve it to him and lie about the brand. He doesn't know the difference... so again, he just thinks he can.
He says he hates lamb and kangaroo as well, and so far that's been true. Whenever I've given him a lamb steak and said it's was beef, he's said it tastes funny and he doesn't like it. I use kangaroo mince sometimes, and he always asks why the beef tastes weird. So at least he's not faking those ones.