Mix all of the dry ingredients (flour, sugar, cocoa, baking soda, salt) with a fork in an ungreased 8"x8" square pan.
Stir in water, oil, vinegar and vanilla. Make sure to scrape the the edges and corners to incorporate all of the dry ingredients.
Sprinkle with chocolate chips.
Bake at 350 degrees for 35-40 minutes, or until toothpick comes out clean. Let cool completely before dusting with powdered sugar, slicing and serving.
Notes
Store leftovers, store in an airtight container at room temperature for up to 3 days.
To freeze, cool cake completely, then wrap tightly with plastic wrap, then foil and place in a freezer bag. Freeze for up to 3 months.
For a richer and deeper chocolate flavor, instead of water use a cup of cooled coffee. You can also use milk for a smoother chocolate taste.
Chocolate frosting (optional): Beat 1/2 cup softened butter, 2 cups powdered sugar, 2 tablespoons cocoa powder, 1/2 teaspoon vanilla, and 1-2 tablespoons milk until fluffy; about 2-3 minutes. Spread over cooled cake.