Preheat the oven to 350 degrees.  For the french toast: Grease a 9-by-13-inch baking dish with butter or nonstick spray. Cut the bread into 16 slices, about 1-inch thick.  In a large bowl, mix together the eggs, milk, cream, sugars, cinnamon and vanilla. Dip slices of bread, four at a time, in the egg mixture. Let each slice rest in the mixture for 1 minute per side (2 minutes total). Once soaked, place the slices in the baking dish, shingling them slightly. Continue until all of the bread has been soaked. Pour any remaining egg mixture over top of the bread and let rest while you make the topping. For the topping: Roughly chop the pecans, leaving some whole. Combine the butter, brown sugar, corn syrup and maple syrup. Once the sugar is dissolved, remove from the heat and stir in the pecans. Place spoonfuls of the mixture all over the top of the bread. Cover and bake for 20 minutes. Uncover and continue baking for 25-30 more minutes, until the egg custard is set and the topping is golden brown. Let rest for 10 minutes before serving. Cut into squares and serve with a drizzle of syrup from the bottom of the pan.