Prepare your ice cream maker as directed by the machine manufacturer. This usually requires freezing the base overnight. In a 4-quart saucepan, combine the fat-free milk, sugar substitute, and powdered milk. If using the vanilla bean, scrape the seeds into the milk mixture (not required but it will add a nice extra boost of vanilla flavor). Bring the milk mixture to a simmer over medium heat, stirring until the sugar substitute and dry milk are dissolved. Turn the heat to low. In a medium bowl, beat the egg yolks for about 2 minutes with a whisk or hand mixer on low speed. Temper the yolks by slowly adding 1/2 to 1 cup of the heated milk mixture to the egg yolks while stirring constantly until blended. Pour the eggs into the heated milk mixture and turn the burner to medium. Stir constantly until the mixture is thickened (like a thin custard). It should be about 170 degrees F. Remove from heat and stir in the half-and-half and vanilla. Let cool slightly, then cover and refrigerate until FULLY chilled. This will take 4-8 hours depending on how cold your refrigerator is. You can let it chill overnight too. When the mixture is chilled you can add in the fruit (if using, see notes below). Combine well. Pour the mixture into the freezer base of your ice cream maker and assemble the machine as directed by the manufacturer. Follow the manufacturer's directions for making the ice cream. cook's notes Chocolate ice cream: add fat-free, sugar-free chocolate syrup to taste while the machine is processing if possible (it blends in better). For best results, puree your fruit first. You can leave some small chunks in but to get even flavor a puree works best. Remove skins, stems and pits before pureeing. Fruit ideas: peaches, berries like strawberries, raspberries, blackberries, blueberries. Chunky fruit preserves work well, they offer a subtle taste while still letting the vanilla ice cream shine through. Almond or other extracts can be substituted for vanilla.