In a heavy-bottomed, 2 quart saucepan, whisk together the cream, milk, 1/2 the sugar, and 1/2 the malted milk powder. Slit the vanilla bean lengthwise, scrape the tiny seeds into the pan, and tossin the bean pod. Bring to boil over moderate heat, stirring occasionally. Remove from heat and allow to steep for 1 hour.
Prepare an ice bath by filling a large bowl with ice and setting a smaller bowl on top.
Whisk the egg yolks in a small bowl with the remaining sugar and malted milk powder. Return the cream mixture to a boil, and remove from heat. Temper the yolks by slowly ladling 1/2 cup of the hot liquid into the bowl with the yolks, whisking constantly. Still whisking, pour the warm yolk mixture back into the hot cream and then stir with a wooden spoon for a few moments to thicken the custard.
Strain the custard through a fine-mesh strainer into the bowl set over ice, and stir occasionally until chilled. Freeze in an ice-cream maker, following the manufacturer's directions.