Article: Fill a large stockpot with 2 to 3 inches (5 to 7.6 cm) of water and bring it to a boil over high heat. Reduce the heat to medium, then sit the steamer basket inside.  The steamer basket should not touch the boiling water directly. After reducing the heat, the water should remain at a simmer. Cover the pot with its lid to prevent the water from evaporating as you prepare the cake batter. Coat an 8-inch (20-cm) round baking pan with nonstick cooking spray or shortening. Lightly flour the bottom and sides of the pan, as well. Alternatively, you can coat the sides of the pan with cooking spray and line the bottom with parchment paper. Combine the butter and sugar in a large mixing bowl. Beat on medium to high speed for several minutes, or until the mixture is light and creamy. Add the eggs to the butter mixture one at a time, beating after each addition.  Make sure that each egg is thoroughly beaten into the mixture after each addition. If you're using small eggs instead of large eggs, you'll need to use three instead of two. Add one-third of the flour to the batter and beat until combined. Add half of the milk afterward, beating again until evenly combined. Repeat this procedure with the remaining flour and milk. Add one-third of the flour and mix it in, followed by the remaining milk. Finish by mixing in the last third of the flour. Drizzle the vanilla extract over the batter. Beat on medium to high speed until incorporated. Pour one-fourth of the batter into a separate small bowl. Set aside the remaining three-fourths for now. The smaller portion of batter will be flavored with cocoa powder and the larger portion will remain vanilla flavored. Sprinkle the cocoa powder into the smaller batch of batter. Mix well by hand or with an electric mixer set to low speed. Pour the vanilla batter into the greased pan, then drizzle the chocolate batter on top. Use a knife to carefully swirl the two batters together without mixing them. This act will create the marbled effect. Tightly cover the top of the cake pan with aluminum foil. Fold the foil under the bottom of the pan to hold it down. The top of the pan must be covered tightly. Otherwise, excess moisture from inside the steamer can get into the batter and ruin the results. Place the cake pan in the center of the preheated steam rack. Cover the steamer and cook the cake for 30 to 45 minutes, or until a toothpick inserted into the center of the cake comes out clean. Keep the steamer over medium heat and avoid lifting the lid as the cake cooks. Each time you lift the lid, some of the heat escapes, which may cause an increase in the overall cooking time. Remove the finished cake from the steamer and let it cool in its pan before turning it out onto a serving platter. Decorate as desired and enjoy.

What is a summary?
Set up the steamer. Grease the baking pan. Cream together the butter and sugar. Add the eggs. Rotate the flour and milk. Mix in the vanilla. Separate the batter. Add the cocoa powder to the small batch. Combine the batters in the prepared pan. Cover the pan. Steam for 30 to 45 minutes. Cool before serving.