Half fill a cooking pot with water and add the beans. Bring to a boil over high heat. Cook for 1-2 minutes then drain beans in a strainer and rinse to remove any foamy residue.
Transfer beans back to the pot. Half fill with some fresh water, add a pinch of salt, and bring to a boil again. Then drop the heat to medium and cook partly covered until beans get soft and tender. It takes about an hour on the stovetop. Alternatively, you may cook the beans in a pressure cooker for about 20-25 minutes.
Once the beans are nice and tender turn the heat off and set the pot aside.
Preheat oven to 200°C / 392°F.
In another cooking pot heat the 6 tablespoons of olive oil over medium heat.
Add the red onion and leek and cook until slightly softened.
Then add the garlic, spring onions, and celery. Cook for 1-2 minutes more for those to soften as well.
Add the mixed greens in batches into the pot. Stir with a wooden spoon. Cook the greens just until they soften slightly. Then turn the heat off and transfer the greens to a 9x13-inch (23 x 33cm) baking dish. Sprinkle the chopped chervil and dill on top.
Using a slotted spoon transfer the cooked beans from the cooking pot to the baking dish (Don't throw away the cooking water). Spreading them evenly over the greens.
Add ½ cup of the water that you cooked the beans in, into the baking dish. Then drizzle with olive oil on top and lemon juice. Season with kosher salt and freshly ground pepper.
Bake for about 30 minutes just until the beans start to get some color on top.
Serve with a good drizzle or raw olive and fresh lemon juice on top and enjoy!