Marsh Cake

Step 1 -Place the eggs, 1 cup of the milk, and the sour cream in a medium bowl and let sit until they come to room temperature, about 30-45 minutes.

Step 2 -Arrange a rack in the middle of the oven and preheat the oven to 350 degrees F.

Step 3 -Coat a 9x13-inch baking dish with 1 tablespoon of the vegetable oil.

Step 4 -In a large bowl, add the all-purpose flour, the brown sugar, the granulated sugar, 1/2 cup of the Dutch-processed cocoa powder, the baking powder, and the baking soda and whisk until combined.

Step 5 -Add the remaining vegetable oil, 1 tablespoon of the vanilla extract, and 1/2 teaspoon of the kosher salt to the egg mixture and whisk until smooth and combined.

Step 6 -Add the wet ingredient mixture to the flour mixture and stir with a wooden spoon or flexible spatula until just combined.

Step 7 -Pour the batter into the prepared baking dish.

Step 8 -Bake until a toothpick inserted into the center comes out clean, about 30-33 minutes.

Step 9 -Transfer the cake from the oven and evenly scatter the marshmallows over the still-hot cake.

Step 10 -Return the cake to the oven and bake just until the marshmallows start to melt, about 2-3 minutes.

Step 11 -Place the baking dish on a wire rack and let the cake cool for 30 minutes.

Step 12 -In a large saucepan over medium heat, melt the unsalted butter.

Step 13 -Add the remaining milk, the remaining Dutch-processed cocoa powder, the remaining vanilla extract, and the remaining kosher salt to the melted butter and whisk until combined.

Step 14 -Slowly sift in the powdered sugar and whisk until smooth, about 1 minute.

Step 15 -Remove the saucepan from the heat and let the frosting cool.

Step 16 -Slowly pour the frosting over the warm cake and spread it into an even layer.

Step 17 -Let the cake sit until the frosting is set, about 30 minutes.

Step 18 -Slice and serve.