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 bay leaf, nutmeg and garlic. Whisk over medium heat until the mixture thickens to sauce consistency and is smooth, about 6 minutes. Stir in the salt and pepper.
Remove and discard the bay leaf and garlic.
Preheat the oven to 450 degrees F. Oil a heavy non-stick 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 cheese on top. Arrange the meatballs, cut-side-down, on top. Sprinkle with Parmesan cheese. 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 for 10 minutes longer until the kale is crispy.
Cut into squares and serve.