Rinse the soaked beans and place them in a large pot. Cover with water, bring to a boil, then simmer until tender. Drain and set aside.
In the same pot, heat olive oil over medium heat. Saut onions, carrots, celery, and garlic until softened.
Add the cooked beans, diced tomatoes, tomato paste, oregano, bay leaf, salt, and pepper to the pot.
Pour in enough water to cover the ingredients. Bring to a simmer and cook for about 1 to 1.5 hours, stirring occasionally.
Taste and adjust seasoning as needed. Remove the bay leaf.
Ladle the Fasolada into bowls and garnish with fresh parsley.