Put the sugar into a pot and add the honey. Allow to boil until the mixture reddens and remove it from the heat.
Beat the egg whites on low heat until they turn to fluffy snow. Add the egg whites to the hot sugar mixture a spoon at a time, while whipping continuously with a whisk. Put the pot back on low heat, making sure the mixture does not thicken too much.
While stirring slowly, add the finely ground walnuts. Lay out a large tray with baking paper and then butter it. Pour in the mixture and then smooth it out carefully by covering the top with another sheet of buttered baking paper and press gently.
Leave it to sit for 1 night as is. The next day, remove the paper. Take a sharp knife, dip it in cold water and cut the halva into squares.