Preheat oven to 400°
Line a baking dish with six to eight slices sourdough bread cut 1/2-inch thick.

Mix the vanilla and cinnamon together first. 
In a separate bowl, whisk grade beaten eggs, whole milk and maple syrup together with the cinnamon/vanilla extract mixture and a dash of salt until thoroughly combined. 
Pour the egg mixture over the sliced sourdough bread and allow the slices to soak for about five to ten minutes.
In the meantime, heat butter and/or oil in a skillet over a medium-high heat until it melts, then reduce the heat to medium before gently adding soaked bread.
Gently fry the bread on one side until it lightly browns, then flip it to fry the other side for two minutes or so.
Place French toast slices on a cookie sheet and dust liberally with powdered sugar.
Bake in oven for 15 to 20 minutes, turning and liberally dusting with powdered sugar again about halfway, until both sides are a dark golden brown.
The powdered sugar should caramelize just a bit to make the bread just a bit crunchy.

Baked Method:
If you wish, you can skip frying the bread in a skillet and do this instead.
Preheat oven to 500°.
Place bread slices on a well greased cookie sheet.
Bake for 5 minutes.
Turn.
Bake for 5 minutes more.

Serve with butter and hot syrup.