Heat oven to 375 degree F.  Loosen the fillet piece from each half-breast; open up like a book so breast lays flat.  Flatten each breast to ¼-inch thickness.  Season with pepper.  Cover and cook 3 cups spinach until wilted (refrigerate remainder for garnish).  Drain.  Rinse under cold water; drain again.  Pat dry and flatten with paper towels.  Place breasts skinned side down.  Cover each with an even layer of spinach.  Mix remaining ingredients and spread evenly over spinach to within ¼-inch of edges.  Roll up jelly-roll style, starting from the shortest end.  Arrange in lightly oiled baking dish, seam down.  Cover with foil.  Bake until chicken is opaque, about 18 to 24 minutes.  Refrigerate 3 hours.  To serve, cut each roll in ½-inch thick slices; arrange on reserved spinach leaves.  Garnish with cherry tomatoes.