Step 1

Step 1 - Rinse and peel the turnips and carrots. Slice them into thin slices ( about 1/4 -inch).

Step 2

Bring a large pot of salted water to a boil. Add the carrot slices and boil for 5 minutes. Add the turnip slices and cook for 20 more minutes, until tender – but not mushy (note: carrots are firmer than turnips so need about 5 minutes extra of cooking). Drain and set aside.

Step 3

Step 2 – Make the Béchamel Sauce.

Step 4

Finely chop the sage leaves. Melt the butter in a heavy-bottomed sauce pan with the sage leaves. When the butter is foamy, add the flour and stir with a wooden spoon until it becomes a dry paste. Switch to a whisk and start pouring in the milk very slowly, in small additions. Whisk continuously until the sauce thickens – make sure there are no lumps left before you start pouring more milk. Add the salt, pepper, nutmeg and Dijon Mustard and whisk again until the sauce is smooth and velvety. Remove from the heat and cover with wax paper to prevent a "skin" from forming on top.

Step 6

Pre-heat your oven to 380°F (193°C) with a rack in the middle.

Step 7

Step 3 – Make sure the carrot and turnip slices are well drained and moisture free. Lay half of the slices across the bottom of a large buttered baking dish, alternating turnips and carrots. Spread about half of the Béchamel sauce over top and sprinkle with salt and pepper to taste. Cover with the rest of the carrot and turnip slices, and finally the rest of the Béchamel sauce. Sprinkle with salt and pepper to taste. Add cheese over top if this, if using.

Step 8

Bake 20-25 minutes. Finish with 1.5 - 2 minutes under the broiler, until the top is golden.

Step 9

Let cool 10 minutes before serving.