BAKED POTATOES AND ONIONS - Lidia

Ingredients

• 2 pounds russet potatoes, peeled and sliced ¼ inch stick
• 4 tablespoons extra-virgin olive oil
• 2 teaspoons kosher salt
• 2 medium onions, sliced ¼ inch thick
• 6 large fresh sage leaves, coarsely chopped
• 1 cup Chicken Stock, Vegetable Stock, or water (see Headnote above)
• 1 ½ cups grated Italian Fontina
• ½ cup freshly grated Grana Padano