Kale Lentil Stew with Mashed Potatoes

Name: Kale & Lentil Stew with Mashed Potatoes
Ingredients: 1 ½ pounds russet potatoes, peeled and cut into 1 1/2-inch chunks; 1 tablespoon extra-virgin olive oil; 1 medium onion, chopped; 2 cloves garlic, minced; ¾ teaspoon salt, divided; ¾ teaspoon ground pepper, divided; 3 cups low-sodium vegetable or chicken broth; 1 (15 ounce) can low-sodium fire-roasted diced tomatoes; ¾ cup red lentils, rinsed; 4 ounces baby kale (5 cups); ½ cup whole milk; 2 tablespoons butter; ⅓ cup grated Parmesan cheese