To make the filling, combine the heavy cream, sugar, and vanilla extract in a large bowl, and whip with a mixer to stiff peaks, about 5 minutes on medium speed. Cover and chill in the refrigerator. Can be prepared one day ahead
Making the Swiss roll:
Preheat the oven to 425ºF. Place a piece of parchment paper on a 17x12 sheet pan, and rub butter on it to grease
In a large mixing bowl, combine flour and salt, set aside. In another mixing bowl, crack in eggs, sugar, and red food coloring (the amount depends on how pink you want it) You can always add a bit more if it's too pale while beating it. Beat them with a mixer (I used stand mixer) on medium speed for 2 minutes then switch to high speed on 3 minutes or until the color turns pale, light, and airy and reach a ribbon stage. That means when you drag and drizzle a spoonful of the liquid, it will maintain its shape for a good 5–10 seconds before settling back into the liquid. Mix in the melted butter
Add the flour mixture into the egg by gently folding them in with a spatula. Spread the batter on the sheet pan. Bake the cake for 5–6 minutes, until springy to the touch.
Place a piece of parchment paper on a flat surface and sprinkle lightly with some powdered sugar. Flip the cake onto the parchment, then gently peel the parchment paper from the cake. Gently roll the cake up into a log while it’s still warm
Let it cool down completely before spreading the filling
Spread the cream all over, leave a 1-inch border around all edges
Roll the cake up gently (leaving the parchment paper behind)
Cut off both ends of the swiss roll (you can eat them)
Place on wire rack
Making the chocolate ganache:
Fill up a saucepan with some water, bring to a boil Place the bittersweet chocolate on a heat-proof bowl (large enough to sit on top of the saucepan) and set on top of a saucepan without touching the water. Once the water comes to boil, lower the heat and let the chocolate melts. Give it a stir every now and then
Assembling the cake:
Pour the chocolate ganache over the cake
Top with some colorful sprinkle and then refrigerate for at least 30 minutes.