In a large bowl, stir together the sugar, flour, cocoa powder, baking powder, baking soda and salt. Add the eggs, milk, oil and vanilla, and mix for 2 minutes on medium speed with a hand mixer. Then stir in the boiling water. Batter will be very thin, almost as watery as water.
2/3 cup (166 grams) granulated sugar, 3/4 cup + 2 tablespoons (115 grams) whole wheat flour, 1/4 cup + 2 tablespoons (42 grams) cocoa powder, 3/4 teaspoon baking powder, 3/4 teaspoon baking soda, 1/2 teaspoon salt, 1 large egg, 1/2 cup (118 ml) milk of choice, 1/4 cup (60 ml) olive oil, 1 teaspoon vanilla extract, 1/2 cup (118 ml) boiling water