For the sauce: In a heavy small saucepan, melt the butter over medium heat. Add the flour and stir constantly for 1 minute. Gradually add the milk, whisking constantly. Add the nutmeg, bay leaf and garlic. Whisk over medium heat until the mixture thickens to sauce consistency and is smooth, 2 to 5 minutes. Stir in the salt and pepper.
Remove and discard the bay leaf and garlic.
For the pizza: Preheat the oven to 450 degrees F. Oil a heavy nonstick 16- by 10-inch baking sheet with olive oil.
Using fingers, spread the dough over the prepared baking sheet into a rectangle shape. Drizzle the dough with olive oil. Spoon the sauce on top and spread evenly leaving a 1-inch border around the dough. Sprinkle the mozzarella on top. Arrange the meatballs, cut-side down, on top. Sprinkle with the Parmesan. Bake for 15 minutes. Remove the baking sheet from the oven and add the kale in an even layer on top of the meatballs. Drizzle with olive oil and sprinkle with salt. Bake until the kale is crispy, 10 minutes longer.
Cut into squares and serve.
Preheat the oven to 400 degrees F.
In a large bowl, combine the breadcrumbs, Parmesan, basil, parsley, milk, tomato paste, salt, pepper, eggs, garlic and onions. Using a wooden spoon, stir to blend. Add the ground turkey and sausage meat. Using fingers, gently mix all the ingredients until thoroughly combined.
Using a 1-ounce cookie scoop or a small ice cream scoop, form the meat mixture into 1 1/2-inch balls (22 to 24 meatballs). Place the meatballs on a heavy nonstick baking sheet, spacing apart. Drizzle with olive oil and bake until cooked through, 15 minutes.