In a large bowl whisk the eggs, milk, orange zest, salt, and vanilla together until completely combined. If your brioche isn’t sliced yet, slice into 1 inch thick slices and then cut those in half into triangles. Arrange the bread in your prepared pan in 2 layer. Pour the egg mixture over the bread, making sure to coat every piece. Cover with plastic wrap and refrigerate overnight to let the egg mixture soak up.
12 hours later, remove the french toast from the fridge and preheat the oven to 350°F. Bake the french toast for about 40 minutes or until the egg mixture is almost set. While the french toast bakes heat Bonne Maman Orange Marmalade in a small sauce pan until it is warm but not bubbling. Take the french toast out of the oven, and use a pastry brush to brush the the top of the french toast, covering it in a thick layer. Place french toast back in the oven and bake for 10 more minutes. Allow to cool before slicing and serving. Enjoy!