Add the ice cream, black cocoa powder, maple syrup and vanilla to a blender. If your ice cream is dense or the blender needs help getting started, add 1/4 cup (60 ml) of the milk. Blend just until completely smooth, adding more milk a little at a time as needed, up to 1/2 cup (120 ml) total. Very light, airy ice cream may not need any milk. Taste and add more black cocoa, if desired. Note that the milkshake may look dark grey at first but gets very close to black the longer it sits.
2 cups (475 ml) vanilla ice cream, up to 1/2 cup (60 to 120 ml) milk, 3 tablespoons (26 grams) black cocoa powder, 2 tablespoons maple syrup, 2 teaspoons vanilla extract