What you'll need:
½ cup butter or margarine at room temperature plus extra for pan
½ cup orange juice
1/3 cup unsweetened cocoa
1 ½ cups sugar
¼ teaspoon salt
1 teaspoon vanilla
1 cup flour, plus extra for pan
1 teaspoon baking powder
¼ cup powdered sugar
A tessellation is a pattern of repeating shapes that extend in all directions and that fit together exactly with no gaps or overlays.
1. Preheat the oven to 350° Fahrenheit.
2. Place all the ingredients except the powdered sugar in a medium mixing bowl.
3. Use an electric mixer to mix all the ingredients together thoroughly.
4. Put some margarine or butter into the pan and spread it around using a paper towel.
5. Dust a spoonful of flour on top of the margarine and tilt the pan back and forth so a thin layer of flour sticks to the margarine.
6. Spoon the dough into the pan and place the pan in the oven. Bake for about 12–15 minutes, when the edges are slightly browned. To test for doneness, poke a toothpick in the middle of the brownies and then pull it out. There should be no dough sticking to it.
7. Allow the brownies to cool in the pan for at least 15 minutes.
8. Then turn the pan upside down on a cooling rack to remove the brownies. Use the knife to cut the large rectangle carefully in half to make two smaller rectangles.
9. Sprinkle the powdered sugar onto one half of the brownies only.
10. Cut the powdered portion into squares. Then carefully cut each square diagonally to form two triangles.
11. Cut the unpowdered side of the brownies the same way: first squares, then triangles.
12. Take one powdered triangle and one plain triangle and place them together to make a rectangle. Continue the tessellation by alternating one powdered triangle with one plain triangle. If you like, you can make a tessellating design like the fish.