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1
Bring a large pot of water to a boil for cooking the pasta.
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2
In the meantime, in a separate pan, cover the potatoes with water and a few big pinches of salt.
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3
Simmer until just tender, somewhere between 30 - 45 minutes, depending on the size of the potatoes.
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4
Drain well, then slice into 1/4-inch rounds, toss gently with a bit of salt.
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5
Set aside.
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6
Melt the butter in a large skillet over medium heat.
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7
Add the leeks and cook until soft, a few minutes.
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8
Stir in the garlic.
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9
Stir in the cabbage, and then the broth.
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10
Season with salt and cook, covered, for a few minutes, or until the cabbage is tender.
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11
Remove from heat and stir in the mustard, then 1/2 cup of the Parmesan cheese, and half of the slivered sage leaves.
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12
Taste, adjust the seasoning if needed, and set aside.
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13
It should taste good on its own, with an assertive mustard flavor at this point.
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14
Cook the pasta in generously salted water until al dente.
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15
Drain and set aside.
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16
Generously butter a 9 x 13-inch (23cm x 33cm) baking dish, or equivalent.
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17
Arrange 1/2 of the noodles evenly in the bottom of the dish.
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18
Layer half the cabbage mixture, half of the potatoes, 1/2 cup of Parmesan cheese, and half of the cubed cheese on top of the noodles.
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19
Arrange the remaining noodles over the cheese and cover with the remaining cabbage, potatoes, and cubed cheese.
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20
Finish with the remaining Parmesan and slivered sage.
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21
At this point you can cover and refrigerate the casserole for up to a couple days, or bake in a 400F degree oven for 45 - 60 minutes - until the top is nicely golden, and it is hot throughout.
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22
Serve hot.
