Preheat the oven to 175 degrees Celsius and grease a 23 x 33 cm baking dish.
Heat a medium saucepan on the stove over medium-high heat.
Put some oil in a frying pan, heat it and add the onions. Fry the onions until golden brown.
Crush and chop the garlic, then mix it with the onions. Mix and cook until fragrant.
Sprinkle flour over onions and mix. Stir briefly, then slowly pour in chicken broth while stirring. Add milk while stirring.
Let the mixture heat and thicken.
Add sour cream, cheese, salt and pepper and mix well. Let the mixture boil until the cheese melts and thickens. Taste the food to make sure it has enough spices.
Add the parsley and mix.
Mix the grated potatoes with the melted cheese in a large bowl, then spread the mixture into the baking dish. Make sure everything is evenly distributed.
Add a little more cheese on top and bake the casserole in the oven for 35 to 40 minutes, until golden brown and bubbly around the edges.
