Drain the soaked beans and soak again for an hour. Wash the chopped pork hocks and drain.
Place beans and pork pata in a big casserole and add water.
Cover and boil for an hour or until the pork hocks is tender. Set aside.
In a separate heavy saucepan, heat olive oil and saute garlic, onions and tomatoes until soft.
Add the pata (including the broth), Chorizo de Bilbao slices, tomato paste and potatoes.
Bring to a boil until the pata and potatoes are tender. Season with salt and pepper. Serve hot.