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1
Preheat oven to 350 degrees F.
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2
Cook the lasagna noodles according to the package directions; drain, rinse immediately with cold water and then drain again; toss with 1 Tbsp olive oil and set aside.
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3
Melt 2 tablespoon butter in a large saute pan over medium-high heat; add the mushrooms and cook until golden, about 5 minutes.
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4
Reduce heat to medium and add the green onions, shallots, and garlic, and saute for 3 minutes.
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5
Add the drained, chopped spinach, white pepper, and salt, stir well and saute for an additional 5 minutes.
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6
Transfer the mushroom/spinach mixture to a bowl and set aside (do not rinse out this pan - we're going to use it again in the upcoming steps).
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7
Over medium heat melt the remaining butter in the previously-used saucepan; add the flour and cook, stirring constantly to keep it from browning.
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8
Gradually add the chicken or vegetable broth, cream, and vermouth; cook, stirring occasionally, until smooth and thickened, about 5 minutes.
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9
As soon as sauce begins to boil, remove it from the heat and season with thyme and basil.
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10
Combine the shredded cheeses together until well mixed.
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11
Butter, oil, or lightly spray the bottom of a 9x13-inch baking pan.
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12
Pour the half-and-half into the bottom of the baking pan.
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13
Lay 4 cooked noodles in a single layer in the pan.
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14
Layer with 1/3 each of the mushroom/spinach mixture and shredded cheeses, then coat with 1/3 of the sauce.
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15
Repeat the process twice, ending with the sauce.
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16
Sprinkle with grated Parmesan (if using).
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17
Cover the pan with foil and bake at 350F for 20 minutes, then remove foil and bake 20 minutes longer.
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18
Remove from oven and let sit 15 minutes before serving.
