In order to properly preserve minnows you would have to gut them, cover them with garlic salt, and keep it in a real warm place for a couple days.
I tried curing them in the past a couple times and no matter how long I left them, they were all mushy and nasty.
One day I was watching a show on the Discovery Channel about mummyfication. They showed a ancient process where the organs of the body was removed, and the body cavity was filled with various flowers and other fragrant herbs. Then the body was completely covered with salt and left in a warm dry place for weeks. Later they came back, broke away all the hardened salt, and the body was perfectly preserved.
They said you must remove the insides, if not, all the juices from the guts will just be drawn out into the flesh from the salt and turn it to rancid goo. I'm sure this applies to fish as well.
So you'd probably need some rather large minnows capable of being gutted. Have you tried freezing them?