Preheat oven to 400. Butter two shallow 2-quart baking dishes. If you’re going to freeze one, use a disposable foil pan. In a large pot of boiling salted water, cook pasta 3 minutes short of al dente; drain pasta and set aside.
2. While pasta is boiling, heat oil over medium-high heat in a large skillet. Season chicken with salt and pepper; cook until opaque throughout, 3 to 5 minutes per side. Halve each piece lengthwise, then thinly slice crosswise. While chicken pan is still hot, toss the mushrooms in and saute until golden brown (3-4 minutes). Use a little extra olive oil if needed.(Since I used left over chicken, I just cooked the mushrooms in the olive oil)
3. In a 5-quart Dutch oven or heavy pot , melt butter over medium. Add flour and garlic; cook, whisking, 1 minute. While whisking constantly, gradually add milk; bring to a simmer. Keep whisking frequently as sauce thickens, about 1 minute more. Add mushrooms and tomatoes; cook 1 minute. Take the pan off the heat and and gradually stir in provolone and 1/2 cup Parmesan.
4. Add chicken and pasta to pot; season with salt and pepper to taste. Divide pasta mixture between baking dishes. If freezing, place remaining parmesan cheese in a zip-top baggie. If cooking, sprinkle on top.
5. Bake, uncovered, until top is golden and bubbling, about 25 minutes. Let stand 5 minutes before serving.
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