12sage leaves(julienned and fried in the bacon fat)
2cupsshredded mozzarella cheese(about ½ pound, 225g, plus some additional to sprinkle over the top)
1cupgrated parmesan cheese
Prepare the baked sweet potatoes by piercing the raw potatoes with a fork all over. Place on a sheet pan and bake at 400 degrees F for 40 to 55 minutes, until tender. Cool slightly. Cut in half lengthwise and scoop the flesh out. Mash the sweet potatoes and measure out about 2 cups into a large bowl.
Add the ricotta cheese, salt, cinnamon, nutmeg, and pepper and blend until well-mixed. Add the flour 1/2 cup at a time until a soft dough forms. Lightly flour a work surface and divide the dough into 6 equal balls. Roll out each ball into a 1-inch wide rope. Cut each rope into 1-inch pieces, flouring them as needed. Roll the gnocchi over the tines of a fork or over a gnocchi board. Transfer the formed gnocchi to a large baking sheet sprinkled with flour. Repeat until you’ve made all of the gnocchi.
These gnocchi can be made in advance and frozen! Put the gnocchi in the freezer while they're still on the baking sheets and freeze until firm, at least one hour. Transfer them to a zip-top bag and freeze for up to two months.
Boil a pot of water to par-boil the gnocchi, and preheat your oven to 375 degrees F.
While the water is coming up to a boil, prepare the bechamel. Over medium heat, melt the butter and add the olive oil. Whisk in the flour and stir until there are no lumps. Cook the flour for 1-2 minutes, whisking constantly. Pour in the milk, whisking until you get a smooth sauce. Season with salt, pepper and nutmeg.
While the bechamel is cooking, you can prepare the bacon and sage. But you can also prepare them in advance!
When the water is boiling, par boil the gnocchi for 1-2 minutes, drain, and add to the bechamel along with the bacon, sage, mozzarella cheese, and parmesan cheese, reserving some of the bacon, sage, and cheese to sprinkle over the top of your casserole if desired. Transfer the entire mixture to a casserole dish, and bake for 35-40 minutes.