Slice the cheese in half and spoon jam on each half, spreading it out evenly. Add the cranberries and pistachios on one half only, pressing down gently to stick them on. Place the other half of the cheese on top and set aside.
In a small bowl, beat egg and milk together; set aside
Lightly flour the work surface and the rolling pin. Roll puff pastry to make it wider, enough to cover the cheese wheel and also decorate it.
Place the prepared cheese wheel on the puff pastry and using a pizza cutter, slice a circle around, big enough to cover the sides of the cheese and some on top; keep the remaining dough on the side. Brush the puff pastry surrounding the brie with the egg wash.
Bring a little piece of puff pastry up before folding another one on top of it and going all the way around creating a wavy pattern; brush the outside with egg wash.
Place the wheel on the remaining puff pastry and cut a round piece of the same size. Put it on top of the cheese and brush with egg wash. Use a cookie cutter of your choice, cut into the remaining puff pastry and place it on top of the circle; brush with the remaining egg wash.
Set the brie on a baking dish lined with parchment paper and transfer to a 425ºF preheated oven. Bake for 15 minutes.
Turn the broiler on for an extra 5 minutes or until the top is golden brown. Serve immediately with crostini or crackers.