Chicken Florentine Flatbread Pizza

Ingredients (15)

• ✓ cooking spray
• + 1 tablespoon butter add to pantry
• + 4 cloves garlic, minced add to pantry
• + 1 tablespoon all-purpose flour add to pantry
• + ¾ cup milk add to pantry
• ✓ ¾ cup grated Parmesan cheese
• + salt and ground black pepper to taste add to pantry
• ✓ salt and ground black pepper to taste
• + 1 (7 ounce) 6x13-inch flatbread add to pantry
• + 1 cup shredded mozzarella cheese add to pantry
• + 1 ½ cups torn fresh spinach leaves add to pantry
• + 1 cup shredded cooked chicken breast add to pantry
• + 3 small tomatoes (such as Campari), sliced add to pantry
• + ½ small onion, thinly sliced add to pantry
• + 1 drizzle olive oil add to pantry