Start making the Bolognese sauce by finely mincing onions, celery, carrots, and garlic in a food processor. Pour 3 tablespoons of oil into a large rondeau pot over medium heat.
Add the minced vegetables and sauté/sweat them for 4 to 6 minutes while frequently stirring. Next, add in the ground pork and beef and cook until it is well browned and cooked throughout.
Deglaze with the white wine and reduce the amount of liquid by one half. Pour in the hand-crushed tomatoes, salt, and pepper, and mix to combine. Simmer over low heat until it's ready to be used.
Once the dough is rolled out, cut each sheet into 9" to 11" long pieces to fit inside of the 13×9 casserole dish. Set it to the side on a clean surface dusted with flour until it is ready.
Make the bechamel sauce and keep it warm over low heat. Boil about 6 to 7 pasta sheets at a time in a large pot of boiling salted water for 20 to 30 seconds.