Gyros in Scheme!

(serve-on (warm 'pita)
    (fry-or-grill 'onions 'tomatos (marinate
       (slice 'lamb) 'olive_oil '(coriander thyme chili garlic)))
    (mix '(yogurt lemons coriander oregano mint)))


Get the best stuff you can; this should be obvious by now.
The oregano, mint, & thyme should be as fresh as you can get it; the coriander should be whole seed.
For the lamb, I recommend a shoulder cut.
Don't skimp on the marinade time: lamb has a funky taste when unaltered, but it can pick up spices really well given time.