In a large pot, heat the olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes until they start to become translucent.

Add the minced garlic and sauté for an additional minute, stirring frequently to avoid burning.

Toss in the chopped carrots, celery, and red bell pepper. Cook for about 5-7 minutes until the vegetables begin to soften.

Add the rinsed lentils, vegetable broth, and spices (cumin, coriander, turmeric, salt, and pepper). Bring to a boil, then reduce the heat to low and let it simmer for about 30-40 minutes or until the lentils are tender.

Stir occasionally to prevent sticking, and adjust seasoning as needed.

While the stew is simmering, place the cubed potatoes in a pot and cover with water. Bring to a boil and cook until tender, about 15-20 minutes.

Drain the potatoes and return them to the pot. Add the butter and milk, mashing until smooth and creamy. Season with salt and pepper to taste.

Once the lentils are tender, adjust the seasoning again if necessary.

Serve the lentil stew hot in bowls, topped with a generous scoop of creamy mashed potatoes. Garnish with fresh parsley if desired.