You find various dishes of shellfish cooked with beans in countries such as Italy and Spain and they are similar in being hearty and cheap, probably designed to feed hungry fishermen and their families. See, for example Cockles and Broad Beans and Cuttlefish and Bean Stew. At the most extreme I've come across a dish in a Galician restaurant which featured beans but no shellfish, but I'm quite sure the beans had been cooked in a good fish stock.
Although I don't know for sure what the origins of this dish are, it does have northern Spain and Galicia written all over it.
When last in Spain I did try to establish which variety of bean alubias blancas are - the literal translation is simply 'white beans'. Just by looking at the packet contents I concluded they were most likely to be cannellini beans but possibly haricot beans. The recipe in "The Best 100 Spanish Recipes", uses haricot beans though I have used cannellini. It doesn't really matter. I even think this would be nice with butter beans - alubias grandes.
It's quite easy to make this dish for large numbers (simply multiply up the ingredient quantities) because the beans can be cooked up ahead of time and reheated before completing the recipe at the last minute - this literally takes a couple of minutes. The step of blending some of the beans to a paste is not essential but it creates a slightly creamier sauce.
As with all shellfish 'stew's a chunk of good bread is always welcome.
Alubias Blancas Con Almejas
Ingredients (serves 2)
Extra virgin olive oil
400g clams, cleaned
100g dried cannellini beans, soaked overnight
1 small onion, half cut into quarters, the other half finely chopped
1 garlic clove, peeled
1 dried bay leaf
50 ml white wine
1 tbsp finely chopped parsley
1 dried red chilli, broken in half (optional)
Sea salt and freshly ground black pepper
Method
Put the beans in a saucepan with the garlic clove, bay leaf and the two onion quarters. Barely cover with cold water and a glug of olive oil. Bring to the boil then simmer gently, covered, until the beans are tender, roughly an hour and a half.
Transfer a couple of tablespoons of beans to a bowl along with two or three tablespoons of the cooking liquor. Using an electric hand blender, whizz the beans and liquor to a paste and return the paste to the saucepan. Season to taste.
In another saucepan heat 1 tbsp extra virgin olive oil and fry the chopped onion and the dried chilli (if using) until the onion has softened, with colour. Add the white wine and bring to the boil. Add the clams, cover with a lid and cook for 2-3 minutes until the clams have opened.
Spoon the clams and most of the cooking liquor (the bottom might be a bit gritty) into the beans, stir in the chopped parsley and serve.
References
"The Best 100 Spanish Recipes", Esperanza Luca de Tena (2005), pp. 51: https://www.amazon.com/Best-100-Spanish-Recipes/dp/8480039205
"Receta de judías blancas con almejas", estoyhechouncocinillas.com, accessed 16 September 2019: https://estoyhechouncocinillas.com/2017/11/judias-blancas-con-almejas.html