In a small pot, heat to low the milk and the basil leaves without bringing it to a boil. In a small bowl place the egg yolks and whisk in a little of the hot milk. Mix really well and then incorporate the temper egg yolks to the pot with the milk. Cook for about 3 to 4 min. stiring all the time for the mixture to thicken a little. Turn off the heat, and strain the mixture while pouring it onto another bowl to get rid of the basil leaves, then let it cool completely.
Pour the half and half, granulated sugar, condensed milk, salt and the previous milk mixture, already cooled down, into the blender, and blend until all ingredients are completely integrated.
Pour this into a tall pan or an ice cream pan, cover it and put it in the freezer overnight for it to get firm.