Combine icing sugar, cocoa powder, vanilla extract, canola oil and 4 Tbsp (60 mL) milk in a large bowl. If frosting is too thick, add milk, 1 tsp (5 mL) at a time, until desired consistency is reached.
Frost top of one cake layer. Place second cake layer on top of first layer and frost top of second layer.
Combine icing sugar, cocoa powder, vanilla extract, canola oil and 4 Tbsp (60 mL) milk in a large bowl. If frosting is too thick, add milk, 1 tsp (5 mL) at a time, until desired consistency is reached.
Frost top of one cake layer. Place second cake layer on top of first layer and frost top of second layer.