- 1. Preheat oven to 350°F. Butter a casserole dish or cast iron pan.
- 2. Heat half the oil in a skillet over medium heat. Add the onion, thyme, sage and cook, stirring frequently, until the onions are lightly caramelized, about 15 minutes.
- 3. Season with half a teaspoon of salt and pepper to taste. Spread in the gratin dish. Return the skillet to medium heat, and add the remaining oil.
- 4. Toss the potatoes in the flour, letting the excess fall away. Add it to the pan and cook until it begins to brown in places on both sides, about 7 minutes.
- 5. Add the parsley, season with salt and plenty of pepper, cook for 1 minute more. Layer the potatoes over the onions, cover with the cheese, then add the Lactel UHT Milk.
- 6. Cover and bake for 25 minutes, then uncover, add the bread crumbs, and bake until the top is browned and the liquid absorbed. Around 25 minutes.