Cover the beans with 8 cups water and soak for 8 hours or overnight. Drain, rinse, and place in a pot with 6 cups fresh water and the bay leaf.
Bring to a boil, skim, then simmer gently for 60 to 75 minutes until tender but still holding shape. Reserve 2 cups bean liquid and discard the bay leaf.
Build the Paprika Base:
Heat oil in a skillet over medium-low heat. Cook onions for 15 minutes until soft and lightly golden. Add garlic for 1 minute.
Stir in sweet and hot paprika, then flour, for 30 seconds. Gradually stir in 1 1/2 cups reserved bean liquid until smooth. Add salt, pepper, and mint.
Bake:
Heat the oven to 400 F (200 C). Combine beans and paprika sauce in a shallow earthenware dish. Add enough reserved liquid to keep the beans saucy and tuck in the dried peppers.
Bake uncovered for 30 to 35 minutes until bubbling at the edges and lightly set on top. Rest 10 minutes before serving.
Notes
Add the paprika off high heat so it blooms without scorching.
The beans keep refrigerated for four days and thicken as they stand; loosen with water when reheating.