Boil the beans until softened in a pot with water. Chop the onion finely and braise it in an oiled pan.
Add the drained beans and braise until all the liquid evaporates. Sprinkle with paprika, spearmint and salt.
Stir and leave to cool. Fill the peppers with the beans and arrange in an oiled oven dish.
Pour in a little water, pour oil over the peppers. Bake in a 392°F (200 °C) oven until the peppers brown and the water evaporates.