10 minutes before you make the crackle top, take the butter out of the fridge. After 10 minutes, cut the butter into small pieces. Add the butter pieces, brown sugar, salt, and pulse in a food processor until almost blended. Add flour and pulse until it looks like curds or pebbles. Pulse in the vanilla. 

Turn the dough out onto a sheet of plastic wrap. Bring the plastic wrap together until the crumbs together. Shape the dough into a disk. Place the disk between two sheets of parchment or wax paper. Roll out to 1/16th of an inch. Keep the dough in the paper and transfer to a baking sheet and freeze for two hours. 

To make the cream puffs, preheat the oven to 425°. Line two baking sheets with parchment paper. 

Bring the milk, water, butter, and sugar to a boil in a medium saucepan over high heat. When it comes to a rolling boil, add the flour all at once. Stir with a wooden spoon. It will come together and pull away from the sides of the pan and leave a film on the bottom and sides of the pan. Keep stirring for another minute. The dough should be smooth. Transfer to the bowl of an electric mixer with the paddle attachment. 

Let the dough cool for a few minutes. Turn the mixer on low and add the eggs, one at time, making sure that the egg is incorporated before you add the next. The dough might look like it isn’t going to come together, but it will. By the last egg, the dough should be smooth and thick.

Add the dough to a piping bag, (you can use a cookie scoop, but I like the piping bag best) and pipe onto the baking sheets, leaving two inches between the puffs. 

Cut out the crackle top into rounds about the same size as the puff. Add a frozen disk to the top of each puff. 

Immediately, place the baking sheets in the oven, reduce heat to 375°. Bake the puffs for 20 minutes, rotate pans from top to bottom, and bake for another 10 to 15 minutes. The puffs will be golden brown, and feel hollow when you tap on them. Cool on a cooling rack. 

Slice the puffs and fill with ice cream and drizzle with chocolate sauce.