A classic frosting, sometimes called “boiled frosting.” Here’s a mention from the May 6, 1932 San Jose News, but the recipe is much older. Here’s a reference to it in The Buckingham [Quebec] Post on Feb. 23, 1912.
But the “seven minute” designation seems to have attached in the late 1920s or early 1930s; for example, this version in the Nov. 8, 1934 Spokane Daily Chronicle.
For the seven-minute frosting, you need 2 egg whites, unbeaten; 1-1/2 cups sugar; 5 tablespoons water; 1-1/2 teaspoons light corn syrup; 1 teaspoon vanilla.
Combine egg whites, sugar, water and corn syrup in top of double boiler, beating with roatary egg beater until thoroughly mixed. Place over rapidly boiling water, beat constantly with roatary egg beater, and cook 7 minutes or until frosting will stand in peaks. Remove from boiling water. Add vanilla and beat until thick enough to spread. This makes enough frosting to cover tops and sides of two 9-inch layers.
Seven Minute Brown Sugar Frosting
Place in a double boiler:
2 egg whites
1-1/2 cups brown sugar
1 Tbsp. light corn syrup
1/4 cup cold water
Cook, beating constantly with beater till peaks form. remove from heat. Add: 1 tsp. vanilla.