Boil the potatoes in lightly salted water, peel them and press them through the potato press. Put aside.
Clean the savoy cabbage, remove the stalk and cut the leaves into fine strips. Cook in salted water and drain well.
Heat the olive oil moderately in a pan, add the garlic and tarragon. After 1 minute, add the savoy cabbage and potatoes and cook for 5 minutes, stirring occasionally. Season to taste with salt and pepper.
Shape the savoy cabbage and potato mixture with the starter rings and serve. Alternatively, form cams from the mass.