How do I make a good, crispy potato crust for a potato-crusted fish dish?

I recently ate at a Bob Evans, and really enjoyed their potato-crusted fish. The basic gist of the recipe is such:

3/4 cups instant potato flakes 1 cup tartar sauce 1/4 cup snipped fresh chives 2 teaspoon grated fresh lemon peel 4 (6 ounces each) fish fillets

Preheat oven to 450 degrees F.

I used tilapia instead of trout, used some fancy tartar sauce I bought at the fish counter, and used Publix instant garlic mashed potatoes, since, for the life of me, I didn't really know what "potato flakes" were. The resulting dish came out very tasty, but without that nice crust to it. I am more than happy to use actual potatoes or even sweet potatoes, tweak the tartar sauce, etc., but I am not sure where to start. What can I do to get a really good crust that you can sink your fork (and your teeth) into? Thanks!