Prepare the ingredients: Peel the potatoes, rinse them, and boil them for fifteen minutes. The potatoes are done boiling if a fork pokes into them without resistance.
Mash the potatoes: Drain the water and mash them with a fork when they are done boiling. Add the cream cheese, milk, and celery salt and thoroughly mix them.
Cook the vegetables and beef mince: Add cooking oil to a preheated pan on medium-high heat. Add the sliced onions and sauté for a minute. Then, add the frozen vegetables and continue to cook for two minutes while stirring occasionally. Thereafter, add the minced beef to the pan. Also, add the beef stock cube, lemon juice, oyster sauce, Worcestershire sauce, salt, and pepper, and stir to mix everything. Make sure to separate the minced beef as it is cooked.
Crescents: Create mini dentures and grooves on top of the mashed potatoes and bake the cottage pie for twenty minutes with the fan on. In an oven without a fan, increase the temperature to 200ºC / 400ºF and bake for twenty-five—thirty minutes. Watch your cottage pie without opening the oven every five minutes to ten minutes.
Transfer and bake the ingredients: Preheat the oven to 180ºC / 356ºF. Transfer the vegetables and the beef mince to a casserole. Then, layer the mashed potatoes on top of the vege-beef fillings.
Serve immediately: Portion out the cottage pie before scooping. Use a spatula to scoop against the casserole from the bottom so that the pie stays in shape.