In a large mixing bowl, beat together the eggs, buttermilk, greek yogurt, canola oil, and vanilla until smooth. Add the flour, sugar, unsweetened cocoa powder, baking soda, baking powder, and salt and mix until there are no longer any clumps of flour. Add the hot coffee and mix until combined. Batter should be pourable, but not super thin. Stir in the chocolate chips, if using.