Place melted butter, sugar, cinnamon, and oats in the bottom of a 13x9-inch baking dish.
Layer apple slices on top of the oat mixture to fill the bottom of the pan.
Layer 8 slices of french bread on top of the apples.
Mix heavy cream, eggs, vanilla, and salt in a bowl.
Pour evenly over the french bread.
Combine 2 Tbsp sugar with 1/2 tsp of cinnamon and sprinkle over the top of the soaked bread.
Cover with plastic wrap and let refrigerate several hours to overnight, until the bread has soaked up all the eggy liquid.
Bake at 350 degrees Fahrenheit for 45 to 50 minutes or until the bread in the center puffs up and is cooked through.
Scoop slices of french toast out, one and a time, and invert them onto a plate so the bottom becomes the top with the oat and streusel mixture facing up.
Drizzle with syrup if desired.