Put the potatoes in a large pan, cover with cold water and bring to the boil. Cook for about 12-15 minutes, until tender. Add the frozen soya beans for the last couple of minutes of cooking. Drain well then tip into a serving bowl.
Toss together the hot potatoes and beans with the crème fraîche and mint and serve warm.
You can use frozen broad beans instead of soya beans, if you like - just add to the potatoes for the last 4 minutes of cooking time. When cooked, you'll need to slip the beans out of their skins before serving.