First, read the English article below.

Prepare a 9-inch (23-cm) baking dish by spraying it with nonstick cooking spray.  You can use a square or oval dish. If you do not have cooking spray, use butter or shortening. Spread the baking spray, butter, or shortening around the dish using a clean paper towel to ensure that the dish is well coated. Add the butter to a medium skillet with high sides and heat over medium heat. Wait until the butter is melted before proceeding to the next step. Add the onion to the melted butter and cook, stirring frequently, until it softens.  The onions may also begin to turn translucent, but they should not be allowed to brown or caramelize. Use a spatula or mixing spoon to stir the onions as they cook. Note that this should only take 2 minutes or so. Sprinkle the flour over the onions and whisk the ingredients together. Cook for 2 additional minutes.  Cooking the flour at this stage prevents the taste of the raw flour from affecting the taste of the sauce. Evenly sprinkle the flour over the onions to minimize the risk of clumps forming. Whisk the milk into the skillet, combining it thoroughly with the onions and flour. Continue cooking until the sauce thickens and bubbles. It should only take a few minutes for the sauce to thicken. Stir frequently with your whisk to check the texture and prevent the sauce from burning to the bottom of the pan. Remove the skillet from the heat and add the cheese. Use a mixing spoon to stir it into the sauce until it melts and distributes itself evenly. Season with salt and pepper, if desired, mixing the seasonings into the sauce thoroughly. Place half of your sliced potatoes in the prepared baking dish and sprinkle with additional salt and pepper, if desired. The potatoes will not be in a single layer, but the layers in the bottom of the dish should be even in order to ensure even cooking. Spoon half of your prepared sauce over the potatoes in the baking dish.  Spoon the sauce over the potatoes as evenly as possible. Give the baking dish a slight shake from side to side to help settle... 

Now, please write a short abstract for it in Chinese. Abstract:
将烤箱预热至350℉（180℃）。 在平底煎锅中加热黄油。 烧制洋葱至其变软。 在面粉中搅拌。 加入牛奶搅拌。 加入四分之三杯（180毫升）奶酪。 将一半的土豆在烤盘中均匀排列。 在土豆片的上面倒入一半酱料。 用剩下的土豆和酱料重复上述步骤。 撒入剩余的奶酪。 烤30分钟。 趁热上菜。