Lasagna can be deceiving while it’s baking: It can look bubbly and golden like lasagna, smell warm and cheesy like lasagna, but when you slice into the middle, it can be cold. “The challenge is to get the middle cooked without burning the outside,” says Francine Maroukian, the author of Chef’s Secrets: Insider Techniques From Today’s Culinary Masters (Quirk Books, $17, www.barnesandnoble.com). To achieve the perfect balance, she suggests keeping an eye on the surface. When the cheese is oozy and melted and beginning to brown, insert a dinner knife or a metal skewer into the middle of the dish. Then remove the knife and lay the tip on your wrist. If the knife is hot, the lasagna’s ready. If it’s cold or just mildly warm, keep baking.