Place the granola in a food processor and pulse it a few times until it breaks down into small crumb sized pieces. If you don't have a food processor, you can place the granola inside a plastic resealable bag and crush it with a rolling pin. Pour the granola into a shallow dish and set it aside for later.
In a bowl, whisk together the eggs, milk, vanilla extract, cinnamon, sugar, and salt until everything is combined and all the sugar has dissolved.
Working in batches, dip the challah slices into the milk mixture and allow it to absorb the liquid for about 15 seconds. Lift the challah out of mixture and let any excess liquid drip off. Place the challah into the dish with the granola. Completely coat both sides with granola.
Heat a pan over medium low heat. For each batch of french toast you cook, use about 1/2 tablespoon of unsalted butter to grease the pan. When the butter has melted, add in the challah. Cook the challah for about 2-3 minutes on each side until the granola has toasted and developed a golden brown color. Remove the french toast from the pan and continue cook the remaining slices. You may need to wipe out the pan with a paper towel after cooking each batch to prevent any small granola pieces from burning.
Serve the french toast with your desired toppings. I topped mine with greek yogurt, honey, and berries. Enjoy!