Look, we are cooking potatoes. We get “fried potatoes”, with one “n”, order. Another case: we roast the potatoes and decided to add mushrooms to it for taste. Then we have a dependent word and we get "fried potatoes with mushrooms", with two "n", but it seems that everything is logical. Or maybe the case when we roasted the potatoes, put it on a plate and decided to add mushrooms. It turns out “fried potatoes with mushrooms”, and here again one “n”. It all depends on when you add the mushrooms.

The root of my problems with Russian is the inability to cook.