Brine the Beans: Place the rinsed beans in a large bowl and cover them with 8 1/2 cups (2 L) water, then stir in the kosher salt and baking soda until combined.
Soak the Beans: Cover the bowl loosely and leave the beans at room temperature for at least 8 and up to 12 hours.
Drain and Rinse: Drain the soaked beans thoroughly, then rinse them well under running tap water to remove the brining liquid.
Heat the Oil: Add 3 tablespoons (45 ml) olive oil to a large pot or Dutch oven and heat over medium heat until the oil is shimmering.
Build the Spice Base: Add the chopped onion, minced garlic, tomato paste, cumin, paprika, turmeric, ginger, kosher salt, and black pepper, then cook, stirring occasionally, until the mixture is fragrant, about 3 minutes.
Add the Lamb: Add the trimmed lamb pieces to the seasoned onion mixture and stir thoroughly to combine.
Combine the Stew: Add the drained white beans, grated tomatoes with their juices, and stock, stirring to distribute the ingredients throughout the pot.
Check the Liquid: Make sure the beans are completely covered with liquid; if they are not, add enough water to just cover them.
Bring to a Boil: Increase the heat to high and bring the stew to a boil.
Simmer the Stew: Reduce the heat to low, cover the pot, and cook for 1 1/2 to 2 hours, stirring occasionally and adjusting the heat as needed to maintain a gentle simmer.
Monitor the Consistency: As the stew cooks, add water as needed to prevent scorching and keep enough liquid in the pot for a stew-like consistency.
Check for Doneness: Continue simmering until the lamb is tender and the beans are fully cooked and creamy.
Season to Taste: Taste the finished stew and adjust the seasoning with additional salt if needed.
Serve the Stew: Ladle the Loubia into shallow bowls and serve with crusty bread on the side.
Finish the Dish: Drizzle the servings with additional olive oil and garnish with chopped cilantro, if desired.