@Mame,
The trick to making them crispy is the double frying. This is how we did it in the restaurant:
1. Fry them once until they just start to turn brown.
2. Cool completely. Doesn't matter how long, just so the inside is cold when you fry them again. This is the secret to crispy.
3. Fry again till they look done.
Crisco will work very well.
Hint: Toss in a large salad bowl with a little salt AND black pepper, for best flavor.