lentil soup with sausage, chard and garlic

INGREDIENTS

• 1/2 cup olive oil, divided
• 4 large links of sweet Italian sausage, casings removed (I used half of this, preferring the sausage to not dominate the soup’s flavor [update] and from the comments, it sounds like most of you preferred it with just 2 links as well)
• 1 medium onion, diced
• 2 celery stalks, sliced or diced
• 2 medium carrots, peeled and sliced into half-moons or diced
• 4 cloves garlic, sliced (reserve half for later in recipe)
• Kosher salt
• A pinch of crushed red pepper flakes (optional)
• 1 cup brown lentils, sorted and rinsed
• 2 bay leaves
• 1 28-ounce can crushed tomatoes
• 6 cups water
• Freshly ground black pepper
• 3 to 4 cups shredded or thinly ribboned Swiss chard leaves or kale
• Grated Pecorino Romano cheese to finish