Prepare the Vegetables: Start by chopping the onion, garlic, carrot, celery, and potato (if using). Set aside.
Sauté the Aromatics: In a large pot, heat the olive oil over medium heat. Add the onion and garlic and sauté until the onion becomes soft and translucent, about 4-5 minutes.
Add the Vegetables: Stir in the carrot, celery, and potato (if using). Cook for another 3-4 minutes, allowing the vegetables to soften slightly.
Add the Spices: Sprinkle in the cumin, smoked paprika, salt, and pepper. Stir everything together for 1-2 minutes to release the spices' full flavors.
Cook the Lentils: Add the lentils and bay leaf to the pot. Pour in the broth and bring to a boil. Once boiling, lower the heat and let the stew simmer, uncovered, for about 30-40 minutes, or until the lentils are tender.
Optional Chorizo Addition: If you’re adding chorizo, sauté it separately in a small pan until crispy, then add it to the pot in the final 10 minutes of cooking.
Check for Seasoning: Taste the stew and adjust the seasoning with extra salt and pepper if needed.
Serve: Remove the bay leaf and ladle the lentejas into bowls. Garnish with fresh parsley if desired.