Preheat oven to 350 degrees F. Grease a 10-cup tube pan or Bundt pan; set aside.
Make the Cake: In a medium bowl, whisk together the cocoa powder and baking soda. Whisk in the boiling water (the mixture will bubble). Add the butter cubes and canola oil and whisk occasionally to melt the butter. Set aside to cool to room temperature.
In a large bowl, sift together the flour, sugars, and salt, then whisk to ensure they are all well mixed.
Add the eggs and vanilla to the cocoa mixture and whisk to combine. Slowly pour the cocoa mixture into the dry ingredients while stirring with a rubber spatula; stop stirring once the mixture has just combined and is free of lumps.
Pour the mixture into the prepared pan and bake until a wooden skewer inserted in the middle comes out with moist crumbs attached, 45 to 50 minutes. Cool the cake in its pan on a wire rack for 30 minutes before inverting it onto a serving plate. Cool completely before glazing with chocolate ganache.
Make the Chocolate Ganache: Place the chocolate in a small heatproof bowl. Place the cream in a small saucepan over medium heat and bring to a simmer, stirring occasionally. Immediately pour the cream over the chocolate. Swirl the bowl to ensure that all of the chocolate is coated with the cream. Cover the bowl with a lid and let rest for 5 minutes. Remove the lid and begin to slowly whisk the mixture, starting with small circles in the middle and working your way outward until you have a smooth, glossy frosting. Let cool at room temperature for 30 minutes.
Place the cake on a serving platter and pour the ganache evenly over the top of the cake. The cake can be kept, covered, at room temperature for up to 5 days.
While this recipe calls for a 10-cup pan, the only ones I have are 12-cup and it seemed to work just fine.
You can make the ganache in advance; store covered at room temperature for up to 3 days. If it has thickened too much to pour, place the bowl over a pan of simmering water and stir until desired consistency is reached.
The recipe only calls for half of the chocolate ganache to be poured on top, but I used the whole thing, because no one every complained about too much ganache ;-)
The cake can also be served warm and sprinkled with powdered sugar, in lieu of the chocolate ganache.