First, make the herb oil. In a food processor or with an immersion blender, blend the parsley and dill with the olive oil. If you have a mortar and pestle, crush the leaves finely. Add salt, pepper, olive oil, and lemon juice to taste.
In the meantime, cook the quail eggs for 2.5 minutes for soft-boiled. Cool them in cold water and set aside.
For the bean spread, place the beans in a sieve and rinse them off. Let them drain well.
Heat some olive oil in a skillet over medium heat. Sauté the onions until they are translucent. Add the garlic, oregano, red chili flakes, and dill, and cook for another minute. Then add the white beans and stir well. Pour in the broth and bring it to a gentle simmer. Let it cook for 2-3 minutes.
Mash the white beans into a puree to your desired thickness. Add more water or broth if needed, and let the beans simmer gently for another two minutes. Set aside to cool.
Spread the white bean puree over the tartines. Drizzle with the parsley-dill oil.
Slice the quail eggs in half and place one half on each tartine. Garnish with watercress, extra chili flakes, and pepper.