heat milk with scraped vanilla bean and seeds in a pan over medium until milk steams. Cover pan, remove from heat, and steep 15 minutes.
Whisk together sugar, cornstarch, and eggs in a bowl until mixed. Strain milk mixture through a fine mesh sieve, then slowly pour warm milk into egg mixture, whisking constantly. Return egg/milk mixture to saucepan over medium heat.
Cook mixture, while whisking, until it slightly thickened, 8 to 10 minutes. If mixture curdles, strain again before transferring to fondue pot. Makes 2 cups. if vanilla beans are too pricey, feel free to substitute 2 teaspoons vanilla extract instead.