Put the oil and butter in a saute pan over medium-high heat. Once the butter has melted, add the crimini mushrooms, garlic, and thyme, saute until golden brown, approximately 5 minutes. Add the balsamic vinegar, season with salt and pepper, toss and remove from heat. Reserve the mushrooms to add to the cooked lentils.
Put the lentils, shallots, garlic, thyme, bay leaves, and water in a pot, bring to a boil, cover and reduce to a simmer, cook until lentils are tender.
Remove the bay leaves, garlic, and shallots, and set aside. Strain the lentils and put in a large bowl.
Puree the garlic and shallots, and add back to the lentils and season with salt, and pepper. Add the sauteed mushrooms and diced tomatoes to the lentils. Toss and garnish with chives.