Heat the olive oil over medium heat in a large oven-safe pan (at least 3 1/2 quarts). Add the mushrooms and let them cook until they have released their moisture and are nicely browned. Season with the salt and pepper and remove them from the pan to a plate.
In the same pan, melt the other tablespoon of butter over medium heat. Add the flour and whisk the two together until they form a paste. Cook the paste for 1-2 minutes. Slowly add the milk and cream to the pan and whisk continuously until the butter and flour are fully incorporated into the milk. Add 1 cup of the parmesan cheese and bring it all to a low simmer. Let it thicken for another minute or so. (see note)
Add the cooked mushrooms, herbs, and uncooked raviolis to the pan. The raviolis should be almost covered with the cream sauce. Sprinkle a 1/2 cup of parmesan cheese over the top.
Transfer the pan to the oven and bake at 375 degrees for 20-25 minutes, or until the ravioli is cooked through and the sauce has thickened.
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Notes
To prevent the sauce from breaking let it lightly simmer. If the pan is too hot and the milk starts to boil the sauce may break. It will still taste fine if it does, but be sure to monitor the heat to avoid this happening. The sauce will be thin before it goes in the oven, but the ravioli will release starch as they bake in it, which will help the sauce thicken.