Preheat the oven to 375°F (190°C).
In a mixing bowl, combine the thawed and drained spinach, chopped artichoke hearts, minced garlic, and grated Parmesan cheese. Blend in the softened cream cheese and half of the shredded mozzarella cheese. Season with garlic salt and black pepper to taste. Set aside.
On a lightly floured surface, unroll the crescent dough sheet. Using a rolling pin, gently stretch it into an 8x12-inch rectangle. Cut the dough into 24 equal squares, approximately 2 inches each.
Lightly grease a mini muffin tin. Place one dough square into each muffin cup, pressing down gently to form a small cup. Spoon about one teaspoon of the spinach-artichoke mixture into each dough cup. Sprinkle the remaining shredded mozzarella cheese evenly over the tops.
Bake for 15-17 minutes, or until the crescent dough is golden brown and the cheese is melted and bubbly.
Remove from the oven and allow the bites to cool in the pan for 5-10 minutes before transferring them to a serving platter. Serve warm.