This simple, beautiful dish surprised me. I thought it would be good, I didn't really expect great. I made it dinner, with stuffed baked mushrooms, but will absolutely serve it as a first course in the future. In exploring other variations online, I ran across a new favorite spanish food blog.
Sauté an onion and some garlic in a whole bunch of olive oil. Then gently fry medium-thick potato slices for a few minutes. Add water (or stock, or many recipes say fish stock or fumet) and salt; simmer until soft; add peas and parsley and heat through.