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1
Heat the olive oil in a large skillet over medium heat.
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2
Add the onion and garlic, and saute until the onion starts to soften, about 4 minutes.
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3
Add the spinach and cook, stirring continuously, until its slightly wilted, about 2 minutes.
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4
Remove the spinach from the pan and let it cool slightly, then place it inside a few paper towels and squeeze out as much liquid as you can.
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5
Give it a rough chop and set it aside.
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6
Turn the heat to medium-low, then, in the same skillet, melt the butter and sprinkle the flour over the top.
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7
Whisk it together to make a roux, then cook it for a minute or two.
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8
Slowly add the milk, whisking out lumps as you go, and cook it until the white sauce is thickened, 4 to 5 minutes.
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9
Turn off the heat and stir in half the basil, half the parsley, and salt and pepper to taste.
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10
Add another 1/4 cup milk if the white sauce is too thick.
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11
Taste and adjust the seasonings.
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12
In a separate bowl, mix together the ricotta, Parmesan, egg, the rest of the basil, the rest of the parsley, and salt and pepper to taste until combined.
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13
Stir in the chopped spinach mixture.
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14
To assemble the shells, use a spoon to fill the pasta shells with the cheese mixture.
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15
Place the shells seam side down in a 9 x 13 casserole dish or disposable foil baking pan.
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16
Pour the marinara evenly over the shells, then ladle the white sauce over the marinara in a zig-zag/line design.
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17
Finally, sprinkle with more Parmesan.
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18
Bake it in a preheated 375 degrees for 25 to 30 minutes, until hot and bubbly.
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19
***To freeze, cover the unbaked shells tightly with heavy foil and freeze for up to 6 months.
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20
To bake the frozen casserole, place it in a 375 degree oven for 1 1/2 hours, then uncover and continue baking for 10 to 30 minutes, depending on how frozen it was.
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21
OR ***Thaw the pan in the fridge for 24 to 48 hours, then bake as directed.
