Adjust your oven rack to the highest level. Begin to preheat the oven to 500ºF.
To make the white sauce, combine the butter and flour in a small sauce pot. Heat the butter and flour over medium-low heat, while whisking, until it begins to simmer. Simmer and whisk the mixture for about one minute.
Whisk the milk into the butter and flour mixture. Allow it to come up to a simmer again, whisking often. When it reaches a simmer, it will thicken. Turn off the heat and whisk in the garlic and salt. Set the sauce aside to cool (it will thicken further as it cools).
Prepare a 12-inch pizza pan with non-stick spray and/or cornmeal. Stretch the pizza dough out to cover the surface of the pizza pan. Pour the white sauce over the surface and spread it out with the back of a spoon. Bake the crust with the sauce for 5 minutes.
Squeeze any excess moisture out of the spinach, then sprinkle the spinach over the surface of the par-baked pizza crust and sauce, followed by half of the mozzarella. Crack the four eggs onto the pizza, equally spaced around the surface. Add a small amount of freshly cracked pepper, then top the remainder of the mozzarella.
Bake the pizza for 10-12 minutes, or until the cheese and crust are golden brown and the eggs are mostly set. Allow the pizza to cool for five minutes before slicing (the eggs will continue to firm up after it comes out of the oven).
*You can use any type of pizza crust you like, but cooking time may vary. The ingredients listed are enough for a 12-inch pizza.