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1
Heat oven to 425 degrees F; butter a shallow 3-quart baking dish.
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2
Cook the pasta according to package directions, adding the broccoli during the last 3 minutes of cooking; drain and return the broccoli and pasta to the pot.
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3
Meanwhile, melt the butter in a large deep skillet over medium heat.
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4
Add shallots and mushrooms and saute until tender, 5 minutes.
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5
In a medium bowl, whisk together milk, flour, salt and pepper.
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6
Pour into skillet and bring to a boil.
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7
Reduce heat and simmer, stirring occasionally, until thickened, about 5 minutes; stir in spinach.
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8
Remove from heat and stir in 1 cup of the fontina and 1/3 cup of Parmesan.
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9
Pour sauce into pot with pasta and broccoli and toss to coat.
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10
Transfer to the prepared baking dish and sprinkle with remaining fontina and Parmesan.
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11
Bake until the cheese melts and is beginning to brown, about 10 minutes.
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12
FIX IT NOW, SERVE LATER:.
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13
After transferring pasta and sauce to baking dish, let casserole cool fr 10 minutes and cover with plastic wrap and refrigerate up to 3 days.
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14
On the night you'd like to serve it, remove casserole from refrigerator and replace plastic wrap with nonstick aluminum foil.
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15
Bake in a 425 degree oven for 30 minutes; uncover and bake until beginning to brown, about 10 minutes.
