Lentil Soup with Apple and Bacon

Name: Lentil Soup with Apple and Bacon
Ingredients: 1 teaspoon canola oil; 6 slices of bacon, chopped; 1 medium leek, white and tender green parts only, thinly sliced; 2 celery ribs, cut into 1/4 -inch dice; 1 medium carrot, cut into 1/4 -inch dice; 2 garlic cloves, minced; 2 tablespoons minced peeled fresh ginger; Kosher salt; Pepper; 1 teaspoon ground cumin; 8 cups chicken stock, low-sodium broth or water; 1/2 cup apple cider; 1 cup green lentils; 1 Granny Smith apple, peeled and cut into 1/4-inch dice; 1/2 teaspoon finely chopped rosemary; Buttermilk, for serving