In a medium pot over medium heat, melt the butter. Add the olive oil, then add in the diced onion. Sauté until softened and translucent. Add the garlic, carrots and celery.
Add in the tomato paste and dijon mustard, and stir everything together. Let this cook for 1 minute before pouring in the red wine. Allow the wine to reduce for a minute or two.
Follow with the chicken stock and drained lentils. Raise the heat to medium-high, and bring the mixture to a boil. Then, lower the heat and add a good pinch of salt, pepper, and the thyme sprigs. Cover the pot and allow it to simmer over low heat for 25 minutes. Just on the level of broth, and if you need more, pour in more chicken stock. Cook for another 10 to 15 minutes, or until the lentils are tender.
Stir in the spinach until it's wilted, then serve with fresh parmesan shavings.
