Step 1: Preheat your oven to 350°F (175°C). Line a 10x15 inch jelly roll pan with parchment paper, leaving an overhang on the sides. Grease the parchment lightly.
Step 2: In a large bowl, whisk together the egg yolks, 1/4 cup granulated sugar, milk, vegetable oil, and vanilla extract until smooth and well combined.
Step 3: Sift the all-purpose flour, baking powder, and salt into the egg yolk mixture. Gently fold until just combined and no dry streaks remain. Do not overmix.
Step 4: In a separate clean bowl, beat the egg whites with an electric mixer on medium speed. Gradually add the remaining 1/4 cup granulated sugar, increasing speed to high. Beat until stiff, glossy peaks form.
Step 5: Gently fold one-third of the egg whites into the yolk batter to lighten it. Then, carefully fold in the remaining egg whites until no white streaks are visible. If using, fold in a few drops of pastel food coloring until evenly distributed.
Step 6: Pour the batter evenly into the prepared jelly roll pan. Gently spread to the corners using an offset spatula. Tap the pan lightly on the counter a few times to release any air bubbles.
Step 7: Bake for 10-12 minutes, or until the cake springs back when lightly touched and the edges are lightly golden. Do not overbake, as this can lead to a dry, crumbly cake.
Step 8: While the cake is baking, lay a clean kitchen towel on your counter and generously dust it with powdered sugar.
Step 9: Immediately upon removing the cake from the oven, invert it onto the sugar-dusted towel. Carefully peel off the parchment paper. Trim any crispy edges if desired.
Step 10: Starting from a short side, gently roll the warm cake and the towel together into a tight spiral. Place the rolled cake, seam-side down, on a wire rack and let it cool completely, about 1-2 hours.
Step 11: While the cake cools, prepare the filling. In a medium bowl, beat the heavy whipping cream, 1/4 cup powdered sugar, and cotton candy extract on medium-high speed until stiff peaks form.
Step 12: Once the cake is completely cool, carefully unroll it. Spread the cotton candy whipped cream evenly over the cake, leaving a small border around the edges.
Step 13: Reroll the cake tightly, without the towel this time. Wrap the finished Swiss roll tightly in plastic wrap and chill in the refrigerator for at least 1 hour (preferably 2-3 hours) to allow the filling to set.
Step 14: Before serving, dust the top with extra powdered sugar. Slice with a sharp, serrated knife and enjoy your whimsical treat!