Heat olive oil in a large skillet over medium heat until it shimmers and begins to gently ripple.
Add the finely chopped onion and carrots to the pan. Sauté, stirring occasionally, until they soften and turn golden around the edges, about 8 minutes. The mixture should smell sweet and earthy.
Add the minced garlic and cook for another minute, until fragrant and slightly translucent. Be careful not to let it brown too much or it will turn bitter.
Stir in the crumbled tempeh or chopped mushrooms, cooking until they develop a slightly browned, chewy texture, about 5-7 minutes. This step enriches the sauce with a meaty, nutty aroma.
Pour in the crushed tomatoes, scraping up any bits stuck to the pan. Bring the mixture to a gentle simmer, and cook uncovered for about 15 minutes, stirring occasionally until the sauce thickens slightly and deepens in color.
Add the cooked lentils, soy sauce or miso, and dried thyme. Stir thoroughly to combine all flavors, then continue simmering for another 10 minutes, allowing the sauce to meld and develop a rich, glossy appearance.
Taste the sauce and adjust seasoning with salt and pepper as needed. If you prefer a thicker consistency, simmer a few more minutes until it coats the back of a spoon nicely.
Remove from heat and let the sauce rest for 5 minutes. This allows flavors to deepen and the sauce to thicken slightly more.
Serve hot over cooked pasta, garnished with fresh herbs if desired. Enjoy a comforting, hearty bowl of vegan bolognese that’s both satisfying and rich in umami flavor.