Slow Cooker Winter Vegetable Soup with Split Red Lentils

extra virgin olive oil

large yellow onion, diced

celery stalks, diced

medium carrots, trimmed, peeled, and diced

medium zucchini, ends trimmed and chopped into 3/4-inch chunks

Yukon gold potatoes, scrubbed and chopped into 3/4-inch cubes

split red lentils

canned chopped tomatoes (with their juices)

pieces of parmigiano-reggiano rind

dried bay leaves

sprigs of fresh thyme

chicken stock

kosher sea salt, plus more

freshly ground black pepper

finely sliced savoy cabbage, reserved for later

extra virgin olive oil, for drizzling

freshly chopped flat-leaf parsley (or basil), for garnishing

freshly grated parmigiano-reggiano cheese, for garnishing