Rinse the lentils in a colander under cold water to remove debris, then place them in a Dutch oven with 8 cups of water, a bay-leaf pinned onion, and a sprinkle of salt. Bring to a boil, then simmer for about 30 minutes until tender.

Chop potatoes into bite-sized pieces and boil them in salted water for approximately 10 minutes until easily pierced with a fork. Drain and set aside.

Heat extra-virgin olive oil in a skillet over medium heat. Sauté the sliced leeks for about 5 to 8 minutes until soft and fragrant.

Stir in minced garlic, fresh thyme, pimentón, cayenne, and saffron. Cook for a few minutes to let spices bloom.

Fold the sautéed leek mixture into the lentils, add the reserved potatoes, and let simmer covered for an additional 10 minutes.

Drizzle with more olive oil and toss with chopped parsley for freshness before serving.