Place one oven rack in the middle of the oven. Preheat oven to 350 degrees. Line two large baking sheets with parchment paper. Set aside.
Whisk together flour and baking powder in a small bowl. Set aside.
In the bowl of a mixer fitted with a paddle attachment, beat eggs, sugar and salt on medium-high until the mixture is doubled in volume, about 6 minutes. Adjust the mixer to low speed and stir in the canola oil and vanilla extract until combined.
While the egg mixture is beating, place the butter in a saucepan over low heat. Add the chocolate and melt, stirring often, until mixture is smooth. Turn off the heat and whisk in the cocoa powder until combined.
Add the chocolate mixture to the egg mixture and mix on low speed until combined. Add the flour mixture and mix until combined. Let the mixture stand for 5 minutes before scooping.
Use a small scoop to scoop tablespoons of dough onto prepared pan, spacing two inches apart. Bake cookies one pan at a time, rotating halfway through baking. Bake until the cookies are puffy, cracked and the edges are set, about 8-12 minutes.
Transfer the pan to a wire rack and let the cookies totally cool on the pan. The cookies are best the day they are baked, but will also keep in an airtight container for up to two days at room temperature.