Preheat the oven to 350. Lightly mist a 12- cup Bundt pan with vegetable oil spray, then dust with flour. Shake out the excess flour. Set the pan aside.
Place the cake mix, sour cream, oil, sugar, almond extract, salt, and eggs in a large mixing bowl. Blend with an electric mixer on low speed for 1 minute. Stop the machine and scrape down the sides of the bowl with a rubber spatula. Increase the mixer speed to medium and beat 2 minutes more, scraping the sides down again if needed. The batter should look well blended. Pour half of the batter into the prepared pan, smoothing it out with the rubber spatula.
Add the cocoa powder to the remaining batter and blend with the mixer on low speed for 1 minute. Pour this evenly over the batter already in the pan. Run a dinner knife through the batters to swirl them together for a marbleized look. Place the pan in the oven.
Bake the cake until it is light brown and springs back when lightly pressed with your finger. 60 to 65 minutes. Remove the pan form the oven and place it on a wire rack to cool for 20 minutes.
Meanwhile, prepare the Frosting:
Sift the sugar and cocoa powder together into a large mixing bowl. Set aside.
Place the marchmallows, butter, and milk in a medium-size heavy saucepan over low heat. Stir until the marshmallows are melted, 3 to 4 minutes. Remove the pan from the heat. pour the powdered sugar and cocoa mixture over the marshmallow mixture. Add the vanilla and stir until the frosting is smooth and satiny.
Run a long, sharp knife around the edge of the cake and invert it onto a serving platter to frost and serve warm. Or invert it onto a rack to cool completely, 30 minutes more. Frost it while the frosting is still warm, spreading the frosting over the top and partially down the sides of the cake with a rubber spatula.