Chop the carrots, celery, onion, and garlic into small pieces.

In a large pot, heat olive oil and sauté chopped onions and garlic until translucent.

Add lentils, canned tomatoes, and vegetable broth; bring to a gentle boil.

Reduce heat and let the stew simmer uncovered until lentils are tender.

Stir in chopped carrots, celery, cumin, paprika, bay leaves, salt, and pepper; continue simmering.

Peel and chop potatoes; boil in salted water until fork-tender.

Drain potatoes, return to pot, add butter and milk, then mash until creamy.

Spoon lentil stew over mashed potatoes and serve.