Prep: Preheat the oven to 350F and line the bottom of a jelly roll pan with parchment paper (make sure the parchment is cut to fit exactly and lays flat). If you don't have a jelly roll pan, your best bet is to use a rimmed cookie sheet instead (cake will be a little longer and flatter, bu still perfectly fine).
Beat egg whites: Beat the egg whites until very stiff peaks form. Set aside.
Beat egg yolks and sugar: In a separate bowl, beat the egg yolks with sugar, water and salt until light in color and fluffy (no need to wash the mixer attachment - the little bit of egg white left on there will help the mix to fluff up!).
Add flour: Add the flour to the egg YOLK mix and beat on the lowest setting until incorporated, about 10-20 seconds.
Fold in egg whites: Add 1/3 of the beaten egg whites to the bowl with the yolk mixture and fold it in to slack down the batter. Add the remaining egg white and very carefully and gently fold in. Take your time with this step! You need to fold in ALL of the egg white (no large flecks of egg white left in the batter, or you’ll get an uneven cake!), but it needs to be done slowly and gently so you don’t knock out the air.
Bake: Evenly spread the batter in the prepared jelly roll pan and bake at 350 for around 15 minutes, or until the cake is lightly golden and springs back when pressed.
Roll and cool the cake: While the cake is baking, spread a kitchen towel on a clean countertop and sprinkle with 1/4 cup powdered sugar. As soon as the cake is done, invert it onto the prepared kitchen towel and carefully remove the baking parchment. Roll up the cake from the short side with the kitchen towel inside. Cool for 2 hours.
Make the Filling:
Beat ingredients: To make the filling, beat the cream cheese until softened. Add the whipping cream, powdered sugar and vanilla and beat on low for 2 minutes or until starting to thicken. Then beat on high until thick and fluffy.
Fill the cake roll: Unroll the cake. Spread with 3/4 of the filling, leaving a small gap around the sides. Evenly spread the diced strawberries on the filling. Tightly roll up from the short side into a cake roll (this time without the kitchen towel!). Make sure the finishing seam is on the bottom. If there is any filling spilling out that’s keeping the end of the cake from sticking to the roll to seal it, carefully scrape it away.
Garnish: Dust the entire cake roll with powdered sugar and garnish with the remaining cream filling and extra strawberries, if you like.