Add Potatoes: Add the potato chunks to the bottom of a 4- to 6-quart slow cooker, spreading them into an even layer so they cook evenly.

Add Beans: Scatter the drained and rinsed butter beans over the potatoes.

Add Fat: Dot the top with the bacon grease, lard, or butter, tucking small pieces down between the potatoes and beans so the fat can melt through the whole pot.

Add Water & Seasoning: Pour in the water, then sprinkle in the salt and black pepper (if using). Gently nudge the potatoes and beans with a spoon to settle everything, but do not stir too hard or you’ll break up the potatoes.

Cook: Cover the slow cooker with the lid and cook on LOW for 6 to 8 hours, or on HIGH for 3 to 4 hours, until the potatoes are very tender and the butter beans are soft and creamy. The broth should look starchy and slightly thickened, with some of the potato edges melting into the liquid.

Check & Stir: Once everything is tender, taste the broth and add a little more salt if needed. Give the pot a gentle stir, just enough to mix the beans and potatoes without mashing them completely.

Serve: Ladle the potatoes, butter beans, and plenty of the broth into bowls and serve hot, right from the slow cooker.