Seafoam Frosted banana cake showcases that shiny, fluffy frosting known as —yep, you guessed it—seafoam. Made from brown sugar and egg whites, the icing is, more or less, a meringue that you slather over a cake. Unlike the traditional meringues for pavlovas and pies, this one is boiled instead of baked. Because it generally cooks for seven minutes, seafoam is sometimes referred to as “seven minute frosting.”

Frosting or candy?

If the name seafoam sounds familiar, but you don’t remember it as an icing, you might be thinking of a candy that bears the same name. A type of divinity candy, it differs from seafoam frosting in that it is boiled until it reaches hard-ball stage on a candy thermometer. Rock hard and riddled with air bubbles, the finished sweet may be coated in chocolate or eaten as is. The origin of the candy’s and icing’s name is unknown.

Make your own double boiler

To make the seafoam icing, you will need a double boiler. Don’t own this cookware? Don’t worry. You can easily cobble one together with a 2- or 3-quart saucepan and a mixing bowl. Fill the saucepan with two inches of water, set it on a burner and turn that on medium-high. Place a mixing bowl on/in the pan. Make sure that it fits comfortably and doesn’t sit in the bubbling water. Add your ingredients and start beating/whisking. That’s all you need to do to make a double boiler and all you need to do to make seafoam frosting.

Seafoam Frosted Banana Cake

Serves 8 to 10

For the cake:

1 stick unsalted butter, at room temperature

3/4 cup firmly packed light brown sugar

3/4 cup granulated sugar

2 large eggs, at room temperature

1 teaspoon vanilla extract

2 ripe bananas, mashed

2 cups cake flour

1 tsp baking powder

1/2 tsp salt

1/2 cup sour cream

For the frosting:

1 1/2 cups firmly packed light brown sugar

1/3 cup cold water

1/4 teaspoon cream of tartar

2 egg whites

1 teaspoon vanilla extract

Preheat the oven to 350 degrees F.  Grease and flour a 9-inch round baking pan and set aside.

Using an electric hand or stand mixer, beat the butter until creamy, 2 to 3 minutes. Add the two sugars and beat again until well-combined.

Add the eggs and vanilla and beat until creamy, about 1 minute. Scrape down the sides of the bowl and add the bananas. Beat again until incorporated, 1 minute.

Sift together the flour, baking powder and salt.

Scrape down the sides of the mixing bowl and add 1/3 of the flour, beating until incorporated. Scrape down the sides and add 1/2 of the sour cream. Continue alternating between adding and mixing in the two ingredients until fully incorporated.

Evenly spread the batter in the prepared pan. Bake for 45 minutes or until a toothpick inserted in the center comes out clean. Remove the cake from the oven and place it on a wire rack. Allow it to cool for 10 minutes before inverting and removing the cake from the pan. Cool completely before icing.

To make the frosting, pour 2 inches of water into the bottom of a double boiler and place the pan over medium-high heat. Place the brown sugar, water, cream of tartar and egg whites in the top of the double boiler and insert the top into the pan. Stir the ingredients together.

Using an electric hand mixer or whisk, beat the ingredients together until glossy and firm peaks form, 7 to 8 minutes. Remove the top pan containing the frosting from the bottom and place on a heat-proof surface. Add the vanilla extract and beat until incorporated. The frosting should be fairly firm but still spreadable.

With an icing knife, liberally spread the frosting over the cake. After the cake has been iced, you can slice and serve it.