1–1/2 tablespoons olive oil
2 large yellow onions halved and thinly sliced
1–1/2 cups chicken or vegetable broth
1/2 – 1 teaspoon Rain’s Choice pure Vanilla Extract (or to taste)
4 tablespoons butter
6 medium-large Russet or 8 large Yukon Gold potatoes, peeled and sliced into thin rounds
2 teaspoons finely chopped parsley
1–1/2 cups Gruyere, Fontina or Havarti cheese, grated
3 tablespoons grated Parmesan cheese
salt and pepper to taste
Preheat oven to 400 degrees F. Heat a large skillet over medium heat, add the oil, and when it’s hot, add the onions. Season with salt and cook, stirring often, until the onions are translucent and soft, about 10 minutes. Turn the heat to high and brown the onions, stirring constantly. Add broth slowly, scraping the bits of onion that have cooked onto pan. Remove from heat. Add vanilla extract.
Grease a 2-1/2 quart casserole dish with 1 tablespoon of the butter, then cut the rest of the butter into small pieces. Create an overlapping layer of potatoes at the bottom of the casserole dish. Cover with 1/3 of the onions, parsley, salt and pepper, and 1/4 of the remaining butter along with 1/4 of the Gruyere or other cheese. Arrange two more layers in the same manner. For the fourth layer, use the balance of the potatoes and butter, and sprinkle on the last of the cheese along with the Parmesan.
Bake until the top layer is golden brown, the potatoes are tender, and most of the broth has been absorbed. Let the gratin cool for 20 minutes before cutting and serving.
For a richer version of this recipe, use 1 cup of broth. After removing from the heat, add 1/2 cup cream to mixture. If the potatoes seem a little dry while cooking, add a little more broth
Find it online: https://vanillaqueen.com/potatoes-gratin/