Grease a 9x13 inch glass baking dish ( I use an large oval glass baking dish). Slice bread and place one even layer into dish, squeezing bread in if necessary; set aside. In a large bowl whisk together the eggs, half and half, milk, cinnamon, nutmeg and vanilla till well combined. Pour mixture evenly over the bread. Cover baking dish with plastic wrap and chill overnight. In morning remove baking dish from refrigerator and uncover. In a small pan melt butter. Add brown sugar, corn syrup and pecans (if using). When all has melted and combined take off heat and evenly pour caramel topping over the soaked bread. Bake uncovered in a 350 degree oven about 45 minutes, or until puffed, bubbly and golden brown. Let sit 10-15 minutes before serving. ( I like to keep a cookie sheet or a piece of tin foil under the baking dish while cooking because once in a while this likes to bubble over on you). Also if you would like it to be extra sticky and gooey double the recipe for the caramel topping.