In a large pot over high heat, bring chicken broth to a boil. Add kale, reduce heat to medium-high, and cook 2 minutes. Add pasta and cook until tender but not soft, 4 to 7 minutes or according to package instructions. While pasta is cooking, use a vegetable peeler to shave cheese into strips about 3 in. long and 1/2 in. wide (strips do not need to be exact).
Just before serving, stir in lemon juice, then divide soup among 6 bowls. Top each bowl with cheese and a sprinkling of chile flakes, if you like.
Note: Nutritional analysis is per serving.