1tablespoonliquid red food coloring1/2 fluid ounce
powdered sugar for dusting
8ouncescream cheeseroom temperature
⅓cuppowdered sugar, sifted1 1/4 ounces
Preheat oven to 350°F/175°C. Coat a 15 x 10-inch jelly-roll pan with non-stick cooking spray (to keep the foil in place). Then line the pan with foil, leaving about a 2-inch overhang at each short end of the pan. Butter and flour the foil, tapping out the excess flour, or use Baker's Joy cooking spray.
In a medium bowl, whisk together flour, cocoa, baking soda, and salt. Set aside. In a small bowl or liquid measuring cup, stir together milk, vanilla, and vinegar. Set aside.
In a large bowl, beat the butter with an electric mixer on medium-low speed for about 1 minute. Increase mixer speed to medium and add the sugar in a steady stream. Beat until light and fluffy, about 2 minutes. Scrape down the sides of the bowl as needed.
With mixer at medium speed, add the egg and mix until combined. At low speed, add 1/3 of the flour mixture, then 1/2 of the milk mixture, mixing after each addition. Add another 1/3 of the flour mixture, the last 1/2 of the milk, then the last 1/3 of the flour, mixing after each addition. Scrape down the sides of the bowl as needed. Add the food coloring at low speed until combined. Without delay, spoon the batter into the prepared pan, spreading evenly with a spatula.
Bake until cake is set and springs back when lightly pressed in the center, about 10 minutes. Remove the cake from the pan by lifting the foil and transfer to a cooling rack. Quickly use a sheet of foil to make a shallow tent over the cake. Let cool for about 45 minutes.
In a medium bowl, beat the cream cheese on medium-low speed until smooth. Mix in 1/2 of the melted chocolate and beat until smooth, then mix in the remaining chocolate until smooth. Add the butter, then the sugar, and beat until smooth and creamy.
Remove the foil tent and transfer the cake to a work surface. Place the cake so one long side is parallel to the edge of the surface nearest you. Using an offset spatula, spread the filling evenly over the cake, leaving a 1/2-inch border along the long edge furthest from you. Begin rolling the cake by gently flipping the edge nearest you over onto itself. Then continue to roll the cake up with gentle pressure. Use the foil to touch the cake as you roll to keep the cake from sticking to your hands.
Place the rolled up cake in its foil across the bottom 1/3 of a long sheet of parchment paper. Bring the top edge of the parchment paper toward you and over the cake roll. Place the edge of a rimless baking sheet, cooling rack, or other long edge at a 45-degree angle to the roll and your surface. Apply pressure to the roll, trapping the edges of the parchment paper. Push the long edge, while pulling the bottom end of the parchment paper toward you to compress the cake roll. This will help eliminate any cracks in the cake.
Carefully lift the cake roll in its foil and set it, seam side down, on a fresh sheet of foil. Wrap the cake in this second piece of foil and place it on a baking sheet or shallow tray. Refrigerate for about 30 minutes.
Remove cake from refrigerator, peel off and discard the foil. Carefully lift the cake onto a serving plate and dust with powdered sugar. Use a serrated knife and sawing motion to cut the cake roll into 1/2- or 1-inch-thick slices. Refrigerate leftovers and cover loosely with plastic wrap to keep cake from drying out.