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1
Preheat the oven to 425F.
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2
Lightly butter a 3-quart au gratin or baking dish; set aside.
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3
Cook pasta according to package directions.
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4
Drain; transfer to a large bowl.
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5
Meanwhile, in a large saucepan combine the squash and 2 1/2 cups of the milk over medium-high heat.
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6
Bring to boiling; reduce heat to medium, and simmer until the squash is tender when pierced with a fork, 18 to 20 minutes.
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7
Stir together remaining 1/4 cup milk and flour; stir into squash mixture.
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8
Bring to boiling; cook until thickened, 2 to 3 minutes.
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9
Stir in 1 1/2 cups of the Gruyere until melted; keep warm.
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10
Meanwhile, in another very large skillet cook chopped bacon until crisp; drain on paper towels.
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11
Crumble; set aside.
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12
Pour off all but 2 tablespoons bacon drippings.
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13
Return skillet to the heat.
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14
Add onions to skillet; cover and cook over low heat 10 minutes, stirring occasionally.
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15
Uncover and increase heat to high.
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16
Cook 4 to 6 minutes more, stirring, until onions are golden.
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17
Mix together with cooked bacon and set aside about 1/4 cup.
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18
Add squash-cheese mixture, onions, and bacon to the bowl with the pasta.
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19
Toss well to combine, then transfer to prepared baking dish.
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20
Mix panko with melted butter & 1/4 cup bacon/onion mixture.
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21
Sprinkle remaining Gruyere and the bread crumbs over pasta mixture.
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22
Bake until top is browned, about 10 to 12 minutes.
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23
Cool 5 minutes.
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24
Sprinkle with parsley if desired.
