Add the diced to pancetta to a cool Dutch oven over low to medium-low heat in order to slowly render the fat. Once you have enough fat rendered to coat the bottom of the pan, you can raise the temperature to medium-low to medium. Cook the pancetta until it is golden brown and crispy, stirring occasionally, 5-7 minutes.
While the pancetta browns, add the olive oil and sliced garlic to a separate pan. Heat over medium heat until the garlic is a light golden brown, being careful not to let the garlic burn. Remove the garlic from the pan and add the kale. Saute for 2-3 minutes until the kale is wilted. Remove from heat and set aside.
Add the pasta to salted, boiling water. Cook 1-2 minutes less than the package directions for a slightly firm bite. The pasta will continue to cook in the oven.
Reserve some of the pasta water before draining in case you need it to loosen the sauce.
Once you have removed the pancetta from the Dutch oven, add the butter and flour to the drippings to make your roux. Whisk the flour and the fat together, cooking for 2-3 minutes just to cook out the flour taste. You don't want to brown it, as that would darken your sauce.
Slowly add in the milk, whisking constantly to avoid lumps. Bring to a low boil, add the pepper, and reduce the heat. Cook for 2-3 minutes to thicken slightly. You want the sauce to coat the back of a spoon. Remove from heat.
... and the pasta. Add the pecorino and parmesan, one at a time, stirring to incorporate. Slowly add in the mozzarella, allowing each batch to melt into the sauce. Add the pasta.
Pour the mixture into a greased 2-quart casserole dish and prepare the topping.
Add the melted butter to the panko bread crumbs, stirring to incorporate well. Stir in the ¼ cup of parmigiano-reggiano.
Sprinkle the topping evenly over the top of the pasta mixture.
Place the casserole in a 350 degree oven and bake for 30 minutes, until bubbly. Allow to stand for at least five minutes before serving.