Chocolate Cake with Marshmallow Frosting

You don't need any excuse to make this easy-to-make chocolate cake with marshmallow frosting for family and friends.
Making the cake: Preheat the oven to 350 ° F. Brush with butter and flour 2 round cake pans 9 inches in diameter and at least 2 inches deep.In a large bowl, using an electric mixer on medium-low speed, combine the flour, sugar, cocoa, baking soda, baking powder, and salt until smooth. In a medium bowl, whisk together the eggs, sour cream, milk, butter, and vanilla until smooth. Mix the egg mixture with the flour mixture on low speed, scraping once or twice from the sides of the bowl, until smooth. Dissolve the espresso powder in 1/2 cup of very hot water and add to the batter. Spread the dough evenly over the molds. Bake, rotating the pans until a toothpick inserted in the middle of the cake comes out clean, 40 to 45 minutes.Let the cakes cool in the pans on a wire rack for 30 minutes. Run a vegetable slicer around the inner edges of the pan and place the cakes on a wire rack to cool completely.Prepare the frosting: Place the egg whites, sugar, tartar, and salt in a large, clean metal bowl set over a saucepan filled with 1 inch of boiling water (keep the water from boiling and the bottom of the bowl from touching the water). Adjust the heat as needed to keep the temperature low. Cook the mixture over medium-low heat, beating with an electric mixer on medium-high speed, until the frosting forms dense peaks, about 7 minutes. Remove the bowl from the heat, add the vanilla and continue to beat until the frosting is glossy and fluffy, another 1-2 minutes.Assemble the cake: If desired, flatten the cake layers with a serrated knife (see instructions below). Place 1 cake, bottom side up, on a serving platter. Spread about 2 cups of frosting evenly. Top with the second cake, bottom side up. Spread the remaining icing evenly over the top and sides of the cake.Freeze like a proFollow these simple steps and people may think you bought dessert from a bakery.Smooth it out in steps.If your cake has a convex surface, use a serrated knife to cut away the bulge, making the top as flat as possible. Before frosting, flip the bottom layer so that it lies on the cut side.Then freeze the middle.Spread the frosting evenly over the first layer using an offset spatula. Don't worry about making it look perfect, as long as it's even. Be careful not to let any crumbs get into the icing. Put a second layer on top and lightly press down.Finish cooking.Spread the icing on the top and sides. To make beautiful curls, swipe the back of a tablespoon over the glaze in a circular motion.