Step 1

For the Wacky Cake: Preheat the oven to 350 degrees. In an ungreased, 9-by-13-inch pan, sift together the flour, sugar, cocoa powder, baking soda and salt. Stir the mixture gently with a fork until combined and spread in an even layer in the baking pan. Make 1 large well in the center of the cake, and 2 small wells on either side of the large one. Pour the oil into the large well, the vanilla into one of the small wells, and the vinegar into the other small well. Pour the coffee evenly over everything in the pan. With the fork, stir everything together until combined.

Step 2

Bake for 25-30 minutes, until a toothpick inserted in the center of the cake comes out clean. Let the cake cool in the pan, on a wire rack, about 1 ½ hours.

Step 3

For the icing: Melt the butter in a small saucepan. Add the cocoa and whisk to combine, then turn off the heat. Add the milk, vanilla, and powdered sugar and whisk all together. Stir in the pecans, if using, and pour, while warm, over the cake.