Lightly toast the sesame seeds without fat and let them cool.
Brush a flat, oven-safe dish with oil. Slice the potatoes very thinly, halve the leek lengthways and cut across into fine half rings, finely grate the ginger and finely chop the garlic.
Mix coconut milk, vegetable stock, ginger, garlic, mace, cayenne pepper and half of the sesame seeds, season to taste and mix with the potato slices.
Put the leek in the pan. Spread the potatoes and coconut milk on top and sprinkle the surface with sesame seeds.
Bake at 220 ° C for 30 - 45 minutes.
Together with a colorful salad, this potato gratin makes a complete meal.