Preheat your oven to 350 degrees. Line a baking sheet with foil and spray with non-stick cooking spray. Place sliced apples onto the prepared baking sheet and bake for 30 minutes.
In a bowl, whisk eggs with almond milk, 1 teaspoon cinnamon, vanilla, and a pinch of salt until fully incorporated.
Dip challah slices one at a time into your egg mixture, using a fork to flip make sure to fully coat the bread.
In a 10-inch or 12 inch skillet,pan, melt 2 tablespoons of butter over medium heat. Once the butter is melted and just beginning to bubble, fry challah slices until golden brown and crisped, then flip and cook the other side.
In a separate small skillet, melt the remaining 2 tablespoons of butter. Add the roasted apple slices into the pan along with the other ½ teaspoon of cinnamon, a pinch of cardamom, a pinch of nutmeg, a pinch of salt, apple cider vinegar and agave. Stir until fully combined.
Stack toasts onto plates, drizzle with spiced roasted apple syrup and top with roasted apples and chopped walnuts.