These are so tasty and work great as a side for just about anything. Be sure to use waxy new potatoes for this, though. Other potatoes will break down too much hile cooking. New potatoes will retain their firmness and shape.
Put the potatoes in a large pot of salted water. Cover and bring to a boil, then lower the heat and simmer until tender (about 15-20 minutes).
While the potatoes are cooking, melt the butter in a frying pan over low heat, then add the scallions and cook, stirring occasionally, until the scallions are softened (about five minutes or so, at most). Add the tomatoes and cook, stirring occasionally, for another 3 minutes.
Drain the potatoes an put them in a serving bowl. Add the cream to the tomato-scallion mixture and bring it to a boil, then add the cheese and stir until it melts. Season the creamy chese sauce with salt and pepper, to taste, and pour over the potatoes. Serve piping hot.