For high altitude adjustments, skip below to the notes section!
Preheat oven to 350°F. Grease and line an 8x8 inch square cake pan with parchment paper and set aside
Stir the espresso powder into the boiling water until dissolved. Add the chopped chocolate to a bowl and pour the hot water/espresso powder mixture over the top. Cover with plastic wrap and set aside.
In a medium bowl, whisk together the yogurt, milk, canola oil, eggs and vanilla. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl with a hand mixer, mix the flour, sugar, cocoa powder, baking soda, baking powder and salt on low speed until combined.
With the mixer on low speed, slowly pour in the yogurt mixture and mix until just combined.
Stir the chocolate and espresso mixture together until smooth. With the mixer on low speed, slowly pour the melted chocolate mixture into the bowl. Mix until just combined. Scrape down the sides as needed.
Pour the batter into the prepared pan and bake for 25 - 30 minutes, or until a toothpick inserted into the center comes out with just a few moist crumbs.
Remove from the oven and cool on a wire rack in the pan for 25 - 30 minutes. Invert the cake to remove from the pan and continue to cool on the wire rack. Frost the cooled cake, slice and enjoy!