Preheat oven to 400.
Line baking sheet with foil and lightly grease with cooking spray; set aside.
Flatten each biscuit-dough with the palm of your hand to about a 4-inch diameter.
Evenly divide shredded mozzarella and add in the center of each dough-disc.
Top with tomato slice (only 1 to 2 slices will fit), and sliced basil.
Season with salt and pepper.
Wrap each dough-disc closed, shaping it into a ball.
Transfer to prepared baking sheet, seam side down, and arrange the rolls so that they are touching each other.
In a small bowl whisk together egg yolk and water.
Brush each roll with egg wash.
Sprinkle a bit of kosher salt and pepper on top of each roll.
Bake for 12 to 14 minutes, or until tops are golden brown.
Remove from oven.