Rinse beans the day before and soak overnight (approx. 12 hours) in 1 1⁄4 l cold water.
The next day peel the onions and garlic. Dice onions, chop garlic very finely. Clean or peel, wash and slice the vegetables. Peel the skin from the chorizo, cut the sausage into slices.
Heat the oil in a large frying pan. Fry all the sausages for 4-5 minutes. Take them out. Fry the onions, garlic and vegetables in the frying fat for 4-5 minutes. Stir in the tomato paste, sweat briefly.
Add beans together with soaking water (approx. 700 ml) and bring to the boil. Cover and simmer for about 1 hour until the beans are soft. Add 100-125 ml water if necessary.
Preheat oven (electric cooker: 225 °C/circulating air: 200 °C/gas: see manufacturer). Fold all sausages under the bean vegetables. Season with salt and pepper. Sprinkle with breadcrumbs and spread butter in pieces on top.
Bake in a hot oven for 10-15 minutes until golden brown.