Add the olive oil to a large pot over medium heat. Add in diced onion, carrot, and celery. Sauté, stirring occasionally, for 5 minutes. Add diced mushrooms and sauté another 3–5 minutes or until veggies have cooked down and are mostly tender. Add in garlic and stir constantly for 1 minute.
Add tomato paste and all the seasonings: dried thyme, dried basil, dried oregano, and dried Italian seasoning. Season to personal preference (I add 1 and 1/2 teaspoons salt and 1 teaspoon pepper). Cook and stir until fragrant, about 1 minute.
Add grape juice and simmer until most of the liquid is absorbed, about 3–5 minutes.
Add diced tomatoes and crushed tomatoes and stir for 1–2 minutes. Add in vegetable broth and the rinsed/picked over lentils. Bring to a boil and add bay leaves. Reduce heat to low, cover, and simmer for 40 minutes. After 40 minutes, simmer uncovered for 5–10 minutes or until lentils are tender and the sauce has thickened. Remove bay leaves and discard. Taste the sauce and adjust seasonings as needed. (I typically add another 1/4 teaspoon salt here.)
Meanwhile, prepare pasta according to package directions. Make sure to generously salt the water (I add 1 teaspoon to every 4 cups of water), since under-salted pasta water will make the whole dish taste under-seasoned. Reserve 1 cup of pasta water, then drain pasta and set aside. Add pasta to a plate or bowl and top with the sauce or emulsify (see next step).
Optionally Emulsify: (see note 1) Place a portion of the Bolognese sauce in the same pot used to cook the pasta. Add hot drained pasta right on top. Toss the pasta and sauce gently for a couple of minutes, slowly adding reserved pasta water as needed until the sauce thickens and generously coats the noodles. Return this emulsified sauce to the rest of the sauce.
Garnish with freshly grated Parmesan cheese and parsley, if desired.
Notes
Note 1: Emulsifying the pasta is totally optional, but if you’re feeling fancy, try it! Toss the finished Lentil Bolognese sauce with reserved pasta water and hot pasta. This is called emulsifying and is one of the secrets to great Italian pasta. It’s how you get a luxurious sauce that coats every bit of pasta. More info here.Storage: Cool the sauce, store in an airtight container, and refrigerate for up to 5 days. To freeze, divide cooled sauce into containers or bags and freeze for up to 3 months. Thaw in the fridge or microwave, reheat in a pot, and add water or broth if needed. Serve hot.