Soak your red lentils in water (at room temperature) for at least 30 minutes (can soak up to 1-hour - I prefer 1-hour soak for softer lentils, but if you're in a time crunch, 30 minutes is just fine too). Make sure the lentils are fully covered under at least extra 2 inches of water. They will plump up and absorb the water. When ready to use - drain and rinse well before adding to the recipe.
Heat the cooking fat in a large pot over medium heat.
Cook the onions low and slow for about 10 minutes, allow them to get soft, and caramelize a little into a golden brown (we want to develop the sweet, rich flavor). Do not let them burn; you can occasionally deglaze with a bit of wine or water to keep them from burning.
Add the mushrooms and carrots and cook for another 5-8 minutes or until all the vegetables are softened and cooked a bit.
Add the garlic, dried oregano, and thyme, and cook for about 1 minute to allow the garlic to be cooked a little.
Add the tomato paste, and cook for 1-2 minutes, stirring frequently to ensure that all vegetables are coated.
Pour in wine (if not using wine, skip this step and increase the broth by wine amount lost) and give it a good stir to ensure that nothing is stuck to the bottom of the pot. Cook for a few minutes to allow the alcohol to be cooked off and let it reduce until all of the vegetables are a jammy consistency.
Add the vegetable broth, crushed tomatoes, red lentils (drained and rinsed after soaking), and finely chopped walnuts.
Cook for 45-60 minutes at medium to medium-low temperature uncovered. You want it at a low simmer to allow the sauce to reduce and thicken and develop in flavor. Give it a good stir every 15 minutes to ensure it isn't sticking or burning. At 45 minutes, the sauce is rich and delicious, but the longer you cook it, the more developed the flavors will be, the softer the lentils get, and the richer and thicker the sauce will be.
Optional nutrition boost: Add fresh spinach leaves and stir them under and let the heat of the sauce soften and wilt them into the sauce
Stir in the balsamic vinegar, fresh parsley, and basil and season to taste with salt and pepper.
If using, you can stir in or simply top with Parmesan or Vegan Cheese