Peel the potatoes and parsnips and cut into 2-3 mm wide strips. Heat the milk and cream in a saucepan and season well with nutmeg and salt. It can be a little salty, the potatoes absorb a lot of salt.
Add the cut potatoes and parsnips to the pot and cook for about 5 minutes. The potatoes should still be slightly firm.
Then put everything in a buttered casserole dish and sprinkle with the grated cheese. The gratin is ready after 15 minutes in the oven at 240 ° C top and bottom heat.