Mix the butter with hot water in a pan, then heat to a rolling boil, shut down the heat and add all of the flour. Beat well, then turn the fire back on to dry out the mixture. Let it all rest for 5 minutes and add eggs, one at a time. Incorporate each egg completely before adding the next. Pipe out profiteroles on a cookie sheet and bake in a 190ºC oven for 50 minutes. Turn off the oven and leave profiteroles until the oven is cool. Crack the oven door a little during this time to enable them to become sufficiently dry. If you are not going to use profiteroles the same day, place them in the freezer immediately. Once they are frozen, store them in a plastic bag to prevent them from becoming stale. Procedure: Cut the profiteroles in half and place them in a high oven until hot. Put a small round scoop of ice cream in each bottom half. Cover with the remaining tops, then ladle thin hot chocolate sauce over the top of each. Serve immediately.