Buttermilk pancake mix, used in the batter of this moist sponge cake roll, is the secret ingredient that makes the cake easy to roll around the fruit filling.
Beat eggs, salt, and vanilla in a large mixing bowl with an electric mixer on high speed about 4 minutes or until thick. Gradually add the 3/4 cup granulated sugar; beat on medium speed for 4 to 5 minutes or until light and fluffy. Add pancake mix; beat on low speed just until combined. Spread batter in a greased and floured 15x10x1-inch baking pan.
Bake in a 400 degree F oven for 8 to 10 minutes or until golden and cake springs back when lightly touched near center. Immediately loosen edges of cake from pan and turn cake out onto a towel sprinkled with powdered sugar. Roll up towel and cake into a spiral, starting from one of the short sides. Cool on a wire rack.
Meanwhile, add rum to peaches; set aside. Beat together whipping cream and the 1/2 cup granulated sugar until stiff peaks form. Unroll cake; remove towel. Drain peaches. Spread cake with half of the whipped cream; top with drained peaches. Spread with remaining whipped cream. Roll up cake. Place seam side down on a serving platter. If desired, sprinkle with powdered sugar. Cover and chill up to 2 hours. Transport in an insulated cooler with ice packs. To serve, cut into 1-inch-thick slices. Makes 10 servings.