from Cook’s Illustrated (March/April 2009, pg. 25)
Updated with pictures.
This is a surprising little cake. And the surprise is mainly because of one ingredient - mayonnaise. NOT “salad dressing,” mind you. No. The real stuff. Mayonnaise. It was a method used in war-times when butter and eggs were scarce; the mayonnaise served as a substitute for those ingredients. This is not a fancy dancy, decorate up with fondant and buttercream icing kind of cake. But it is definitely simple enough for a week-night dessert.
1 1/2 cups (7 1/2 ounces) all-purpose flour
1 cup (7 ounces) sugar
1/2 teaspoon baking soda
3/4 teaspoon table salt
1/2 cup (2 ounces) Dutch-processed cocoa powder (or “Special Dark”)
2 ounces dark, bittersweet or semisweet chocolate (chopped fine)
1 cup hot coffee (or equivalent mixture of hot water and espresso powder)
2/3 cup mayonnaise
1 large egg
2 teaspoons vanilla extract
You will also need:
8 inch square cake pan
Non-stick cooking spray
1 large mixing bowl
1 small-medium mixing bowl
Confectioners’ (powdered) sugar for garnish
Preheat oven to 350 degrees F and prepare cake pan by spraying with non-stick cooking spray.
In large mixing bowl, whisk together flour, sugar, baking soda and salt. In smaller bowl, combine cocoa powder and chopped chocolate; pour hot coffee over cocoa/chocolate mixture and whisk until smooth. Let this mixture cool for several minutes then whisk in mayonnaise, egg and vanilla. Pour mayonnaise/chocolate mixture into flour mixture and stir until combined.
Scrape batter into prepared pan and smooth it all around. Bake for about 30-35 minutes or until toothpick comes out with few crumbs attached after being inserted into the center of the cake. Note: the cake will have a nice rounded domed middle and cracks on the top. This is normal.
Allow cake to cool in pan on wire rack for 1-2 hours. Turn cake out onto serving platter and dust with confectioners’ sugar to serve.