Preheat oven to 350°F.

Lightly grease 18 x 13-inch rimmed baking sheet, line with parchment paper, and lightly grease parchment. Set aside.

In a large bowl, whisk together flour, cocoa powder, sugar, baking powder and salt. Whisk in egg yolks, oil, coffee, and espresso powder until a smooth batter forms.

Using a stand mixer with whisk attachment, whip egg whites and cream of tartar on medium-low speed until foamy, about 1 minute. Increase speed to medium-high and whip until stiff peaks form, 1 1⁄2 - 2 minutes. Transfer 1⁄3 of whipped egg whites to batter and whisk gently until mixture is lightened. Using a rubber spatula, gently fold remaining egg whites into batter.

Pour batter into prepared sheet tray and spread evenly with offset spatula. Firmly rap sheet tray on counter 3 times to remove large air bubbles from batter. Bake in preheated oven until cake springs back when pressed lightly in center, 12-14 minutes. While cake bakes, soak clean dish towel in water and wring out thoroughly. (Do not use a thick or fluffy kitchen towel for this, as you do not want lint in your pumpkin roll. Use a tea towel or flour sack towel. You’ll use this to roll up the cake.)

Transfer sheet tray from oven to wire rack. Immediately run knife around edge of sheet, then carefully invert cake into 2nd wire rack. Carefully remove parchment. Lay damp towel over cake and invert first wire rack over towel. Invert cake and remove rack from top. Starting from short side, gently roll cake and towel together into jelly roll shape. Let wrapped cake cool on rack, seam side down, for 1 hour.

Prepare Espresso Simple Syrup: Bring espresso, sugar, and water to a boil in a saucepan, stirring to dissolve sugar. Let cool.

Prepare the Filling: In a bowl of a mixer fitted with a whisk attachment, whip room temperature butter, stopping to scrape the bottom of the bowl several times, until it has tripled in volume, and is light and fluffy, about 5 - 7 minutes. Add the sweetened condensed milk in thirds, whipping for about 5-10 seconds after each addition. Don't forget to scrape the bottom of the bowl after each addition.

Assemble Coffee Roll: When cake is completely cooled, gently unroll cake with short side parallel to counter edge (innermost edge of cake will remain slightly curled; do not flatten).

Brush espresso syrup over side of cake that is facing up. Don’t wet the cake too much. You’ll have leftover syrup. Spread filling evenly over cake, leaving 1⁄2-inch margin on each short side. Reroll cake, leaving towel behind as you roll. Wrap in plastic wrap and refrigerate for at least 20 minutes or up to 2 days.

Just before serving, brush top and sides of coffee roll lightly with espresso simple syrup. Trim both ends off cake and cut into thick slices by dipping a sharp knife into very hot water and wiping dry between cuts. Serve with an extra dollop of sweetened condensed milk filling.

Cake can be covered in plastic wrap and refrigerated for up to 5 days. Let sit at room temperature for 30 minutes before serving. Espresso syrup can be refrigerated in an airtight container for up to 2 weeks.

Cake can be made ahead of time and frozen up to one month. Remove about an hour before serving to allow cake to reach room temperature.

Recipe by our friend Kim at Kick Ass Baker