Have ready a fine-mesh strainer suspended over a medium bowl containing the finely chopped chocolate.
In a medium bowl, whisk together the sugar, malt powder, cocoa, salt, and espresso powder.
In a medium saucepan, with a silicone spatula, stir together the milk, 116 grams (1/2 cup/118 milliliters) of the cream, and the egg yolks. Stir in the glucose (or corn) syrup and the sugar mixture until the sugar has almost completely dissolved.
Heat the mixture on medium-low, stirring constantly until slightly thicker than heavy cream. When a finger is run across the back of the spatula it will leave a well-defined track. An instant-read thermometer should read 170° to 180°F/79˚ to 82˚C.
Immediately pour the mixture into the strainer, scraping up the thickened mixture that settles on the bottom of the pan. Press it through the strainer and scrape any mixture clinging to the underside into the bowl.
Stir until the chocolate has melted. If little specks of chocolate are not desired, strain again. Then stir in the remaining 2 cups (464 grams) cream and the vanilla. Cover and refrigerate for a minimum of 8 hours or until no warmer than 43˚F/6˚C. (Alternatively, cool in an ice water bath.) Set a covered container in the freezer.
Churn the chocolate malt custard in the prechilled ice cream maker. Transfer the ice cream to a covered container. Press a piece of plastic wrap on top, cover it, and allow it to firm in the freezer for about 4 hours before serving.
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