1/2 cup vegetable oil, plus more for the pan
1 1/4 cups all-purpose flour, plus more for the pan
3/4 cup plus 2 tablespoons granulated sugar
1/2 cup plain malted milk powder (such as Carnation)
1/4 cup unsweetened cocoa powder, plus more for topping
1/2 teaspoon baking soda
1/2 teaspoon ground cinnamon
1/4 teaspoon ground allspice
1/4 teaspoon freshly grated nutmeg
4 large eggs, separated
1/2 cup milk
2 tablespoons confectioners’ sugar
3 cups confectioners’ sugar
1 cup butter
1 teaspoon vanilla extract
1 to 2 tablespoons whipping cream
Make the cake: Preheat the oven to 350 degrees F. Lightly brush an 11-by-17-inch rimmed baking sheet with vegetable oil and line with parchment paper. Brush the parchment with oil and dust with flour, tapping out the excess. Whisk the flour, 3/4 cup granulated sugar, the malted milk powder, cocoa powder, baking soda, cinnamon, allspice and nutmeg in a medium bowl; set aside. Beat the egg whites in a large bowl with a mixer on medium speed until foamy, 1 to 2 minutes. Increase the mixer speed to medium high and gradually add the remaining 2 tablespoons granulated sugar; continue beating until stiff shiny peaks form. Set aside.
Beat the vegetable oil, egg yolks and milk in a separate bowl with the mixer on medium speed (no need to clean the beaters). Reduce the speed to low and beat in the flour mixture until just combined. Fold one-third of the beaten egg whites into the batter, then fold in the rest until incorporated. Pour the batter onto the prepared baking sheet and spread evenly with a rubber spatula. Bake until the cake pulls away from the sides of the pan and springs back when lightly pressed, 12 to 14 minutes. Dust the cake with the confectioners’ sugar and spread a large clean kitchen towel (not terry cloth) on top. Invert a cooling rack onto the towel, then invert the cake onto the rack; peel off the parchment. Roll up the cake and towel together, starting from a long side to form a 17-inch-long roll. (You’ll remove the towel later.) Set aside on the rack to cool completely.
Make the frosting: In a standing mixer fitted with a whisk, mix together sugar and butter. Mix on low speed until well blended and then increase speed to medium and beat for another 3 minutes. Add vanilla and cream and continue to beat on medium speed for 1 minute more, adding more cream if needed for spreading consistency.
Unroll the cooled cake and spread with 1 1/2 cups of the frosting. Gently reroll the cake (without the towel) and trim the ends. Cover with the remaining frosting; dust with cocoa powder.