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1
Preheat the oven to 350 degrees F. Spray a 9 by 9-inch baking dish with cooking spray.
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2
In a small pot, heat the milk with the thyme over medium-low heat until hot.
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3
In a medium saucepan over medium heat, melt the butter with the canola oil.
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4
Add the garlic and cook 1 minute.
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5
Add the flour and cook stirring constantly until the flour is lightly golden brown, about 2 minutes.
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6
Slowly whisk in the hot milk.
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7
Bring the mixture to a simmer and cook until very thick.
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8
Stir in the Cheddar, pumpkin pie spice and salt and pepper to taste.
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9
Coat the bottom of the prepared baking dish with a thin layer of the sauce.
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10
Place one layer of carrots slightly overlapping in the bottom of the baking dish.
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11
Top with an overlapping layer of the parsnips.
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12
Pour a third of the sauce over top.
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13
Repeat with two more layers each of the carrots and parsnips, ending with the sauce.
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14
In a small bowl, stir together the breadcrumbs, Parmesan, parsley and salt and pepper to taste.
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15
Evenly sprinkle over the top of the gratin.
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16
Bake until the gratin is bubbling and the topping is browned, and when pierced through the vegetables yield easily, about 1 1/2 hours.
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17
If the top begins to brown too quickly, cover with foil.
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18
Let rest for 10 minute before serving.
