Wacky Cake

http://www.cookistry.com/2013/02/sort-of-wacky-cake.html

Ingredients
1 1/2 cups (6 3/4 ounces) all purpose flour
1/4 cup cocoa
1 1/4 cups sugar
1 teaspoon baking soda
1/2 teaspoon salt
1 cup water
1 tablespoon balsamic vinegar*
1/4 cup cooking oil
1 teaspoon butter vanilla emulsion (or vanilla extract)
1 egg
1/2 cup semisweet chocolate chips (or as desired)

Preheat your oven to 375 degrees and spray an 8- or 9-inch square cake pan with baking spray.
Combine cake flour, sugar, cocoa, baking soda in a bowl and whisk to combine. If your cocoa is a little lumpy, you can run it through a sifter, if you like.
Mix the vinegar and water together in a cup or small bowl.
Add the vinegar-water mixture, oil, butter-vanilla emulsion, and egg to the dry ingredients. Stir to combine well.
Pour the mixture into the prepared pan, smooth the top of the batter. Bake at 375 degrees until the top springs back when lightly touched, and a toothpick inserted in the center comes out clean. Start checking it at about 35 minutes - the actual baking time will vary a little depending on the pan you use.
Remove the cake from the oven and sprinkle the chocolate chips on top of the cake. Wait about a minute, then spread the now-melted chocolate over the cake to frost it.
Let the cake cool completely before serving. I served it straight from the pan. It's that kind of cake.
*I used a vanilla fig vinegar for this, but a plain balsamic vinegar would be fine. You don't need a high-quality balsamic, but if you have a flavored vinegar that you think would pair well with chocolate cake, you can use that. A raspberry or pear balsamic would be fine. Anything with herbs would be a little iffy.