Place 1 1/2 pints of ice cream, malt powder, and 4 ounces chocolate sauce in a blender and blend until smooth. Pour shakes into 2 tall glasses, leaving a little room at the top. Place an extra scoop of ice cream on top of each shake and drizzle the remaining 2 ounces chocolate sauce over. Garnish with a large dollop of whipped cream and some chocolate shavings. Serve immediately.