Preheat oven to 200°F/400°C and place an ovenproof dish or baking sheet in the oven (this is to keep the finished pan perdu warm).
Make the peaches:
To a large frying pan add the butter over medium-high heat. When melted add the peaches and cook with the flesh side down until they start to brown, turning as necessary. Drizzle over the caramel sauce. Put in an ovenproof dish and keep warm in the oven. Clean out the pan.
Make the pain perdu:
To a shallow bowl add the eggs, vanilla and salt, mix to combine.
Add the 4 tablespoons butter to the same pan over medium heat.
Add a slice of bread to the egg mix and allow to sit on each side for 1 minute, allow excess to drip off. Place in the melted butter and cook for 3-4 minutes or until browned on the bottom, flip and cook until browned on the other side, place in the oven. Repeat with the rest of the bread slices.
To serve:
Place a slice of the pain perdu onto a plate and top with ¼ of the peaches, more caramel sauce if needed and a dollop of whipped cream.