Begin by chopping onions, carrots, and celery into small pieces. Rinse your lentils under cold water until they run clear. Slice the mushrooms and mince the garlic. Gather all your ingredients, ensuring you have vegetable broth, tomato paste, bay leaves, and thyme ready to go.

In a large pot, heat a splash of olive oil over medium heat. Once shimmering, add the chopped onions, carrots, and celery. Sauté for about 5-7 minutes, stirring occasionally, until the vegetables soften and the onions turn translucent.

Stir in the sliced mushrooms and minced garlic to the pot. Cook for an additional 4-5 minutes until the mushrooms have released their moisture and shrunk in size.

Next, mix in the rinsed lentils and tomato paste. Stir thoroughly for about 1-2 minutes.

Pour in the vegetable broth, toss in the bay leaves and thyme, seasoning with salt and pepper to taste. Bring to a gentle boil, reduce the heat to low and cover. Let it simmer for about 25-30 minutes.

Once the lentils are cooked, remove the pot from heat. Stir in the fresh spinach until it wilts, about 2-3 minutes. Optionally, add a splash of lemon juice for brightness.

Ladle the stew into bowls, ensuring each serving includes plenty of mushrooms and lentils. Serve hot.