• Preheat your oven to 400ºF with the oven rack in the center. Line a ¼" sheet pan (9x13") with parchment paper.

Roll Cake Pattern

• Cream together butter, flour, sugar and egg whites with a whisk attachment until smooth. Add in your food coloring and mix until cohesive in color.
• Place batter into a piping bag or plastic baggie and snip off the tip. Pipe your pattern onto the parchment paper and then freeze while you prepare your roll batter (about 20 minutes)

Roll Cake Batter

• Fill your saucepan with 2-3" water and bring to a boil over medium high heat until boiling then reduce heat to medium or until water is simmering
• Place eggs, sugar and salt into the mixing bowl and blend together with a whisk
• Place the bowl with mixture on top of your simmering water. Using your whisk, stir the egg mixture slowly until the sugar granules dissolve (about 110ºF) Remove from the heat.
• Attach your bowl to your stand mixer with the whisk attachment. Add in your vanilla and whisk on high for 2-3 minutes until you reach the ribbon stage (see notes). The mixture should triple in volume and lighten in color.
• Sift in ⅓ of your flour mixture and fold (see notes) the flour in gently without damaging the structure of your egg mixture. Repeat two more times with the flour until just combined.
• Spread batter evenly into your prepared sheet pan and spread with an offset spatula or knife all the way to the edges of the pan. Do not grease your pan.
• Bake for 8 minutes and then remove from the oven and place onto a cooling rack
• Immediately use a paring knife to carefully cut the edge of the sponge away from the sides of the pan. Dust the surface with powdered sugar. Place another piece of parchment on top of the cake, then another cooling rack and flip over to release the cake from the pan.
• Remove the parchment paper carefully and dust the surface with more powdered sugar.
• Place a tea towel over the top of the cake and carefully roll into a spiral. Place into the fridge to cool for one hour before filling with frosting.

Stabilized Whipped Cream

• Sprinkle your gelatin over the water and let bloom for 5 minutes. 
• Melt gelatin for 5 seconds in the microwave. If not fully melted do another 3 seconds. You can tell gelatin is melted when there are no granules of unmelted gelatin visible. Add in 1 teaspoon of cream and stir to combine
• In a cold mixing bowl, whip your heavy cream to soft peaks. Add in your powdered sugar and vanilla.
• Turn your mixer down to low and drizzle in your gelatin and mix until whipped cream forms firm peaks (but not curdled)

Roll Cake Assembly

• Carefully unroll your cooled sponge. It may crack a little towards the very center of the spiral and that is normal.
• Spread a thin layer of your whipped cream and layer chopped fresh fruits like strawberries or blackberries or even mix together if desired.
• Carefully roll your cake back up. Cut the ends of the roll cake off so they look nice and clean and then transfer to a platter.
• Dust the surface of the roll cake with more powdered sugar, swirls of whipped cream and more fresh berries.
• Serve chilled. It will last for three days covered in the fridge.