In a large pot, heat 2 tablespoons of the olive oil over medium-high heat. When hot, add the sausage, stirring occasionally until it begins to brown, about five minutes.
Add the onion, celery, carrots, first two minced garlic cloves, and a pinch of salt. Cook until the vegetables start to soften, another 5 minutes.
Add the lentils, bay leaves, tomatoes, stock, and water. Add a big pinch of salt, and black pepper to taste. If you’re using homemade unsalted stock, you’ll want more salt than if your stock is salted already.
Bring to a simmer, cover partially with a lid, and allow to cook until the lentils are tender, about 30 minutes.
Taste the soup halfway through and add more salt if it needs it. Mine always needs a couple more big pinches of salt since I use unsalted stock. If the soup looks too thick, add a little more water as it’ll continue to thicken as it cools. I like it on the hearty, chunkier side.
When the soup is almost done, combine the remaining two cloves of minced garlic and remaining two tablespoons of oil in a small microwave-safe bowl.
Microwave on high power for 3-5 minutes, I always check it at 3. Stir with a heat-resistant rubber spatula, scraping down sides of the bowl. You want the garlic to turn only lightly golden, as it will continue to cook in the hot oil once it’s removed from the microwave.
To serve: Remove the bay leaves from the soup. Ladle soup into shallow bowls and top with the pecorino cheese, a teaspoon of the fried garlic and oil and a few cracks of black pepper. This soup freezes well and leftovers will keep for several days in the fridge!