Peel the small potatoes and cook them whole in salted water for 20 minutes. In the meantime, clean the chanterelles, but do not wash them, cut off the ends of the stems and cut large mushrooms in half lengthways and crossways. Cap the small red onions and the cloves of garlic at both ends, peel and cut into very small pieces. Wash the celery, pluck the leaves and chop finely.
Drain the water, add 2 tablespoons of the butter to the potatoes and toss with the lid without adding heat. Add 1 tbsp of the celery leaves and keep warm.
Melt the remaining butter in a pan and fry the onion pieces until translucent, add the chanterelles and stir-fry for 3 minutes. Season to taste with the appropriate ingredients, add a tablespoon of the celery leaves. Mix well again.
Arrange the mushrooms together with the potatoes on a serving plate, garnish with the remaining celery leaves and serve warm.