Combine sugar, egg whites, and syrup in top of a large double boiler; add water, and beat on low speed of electric mixer for 30 seconds or just until blended.
Place over boiling water; beat constantly on high speed of electric mixer about 7 minutes or until stiff peaks form. Remove from heat.
Add crushed peppermint, and beat 2 additional minutes or until frosting is hick enough to spread. Spread frosting on cooled cake.
Note: Additional crushed peppermint may be used to garnish frosting.