In the open flame of a gas burner or under a pre-heated broiler, roast the long green chiles, turning them, until they are lightly but evenly charred. Steam the chiles in a paper bag, or in a bowl, covered with a plate, until cool. Rub away the burned peel. Stem and seed the chiles and coarsely chop them. There should be about 3/4 cup. In a large skillet over medium-low heat, melt the butter. Add the ham cubes and cook them, stirring constantly, until lightly browned, about 10 minutes. Sprinkle the flour over the ham cubes and cook, stirring constantly, for 5 minutes. Slowly whisk the milk into the ham mixture. Stir in the green chiles and salt. Raise the heat to medium and bring the milk mixture to a simmer. Cook, stirring occasionally and scraping the bottom of the pan, until thickened into a medium gravy, about 7 minutes. Adjust the seasoning. Arrange the biscuits, split-sides up, on 8 plates. Spoon the gravy over and around the, using it all. Serve immediately. NOTE: I tend to add a bit more "heat" by adding some fresh jalepeno, cut into very fine julienne as garnish to each persons serving. Looks pretty, too. This is also a good dish to make using smoked turkey (thigh) instead of ham.