I'd say, the Queen of Russian food is potato. Honestly, I can't imagine a dinner or supper without it in some form. For soups (borsch, shtshi, other soups), you need it. For the second course, you need it as a garnish - boiled, fried, or in the form of purée. Although some people prefer rice, buckwheat or pasta as a garnish. But I, personally, would never eat pasta if I can choose among pasta and potato. I would never prefer rice or buckwheat either.

By the way, there is a proverb in Russian which says "Potato is a second bread". I wonder is it only Russian?