Prepare a 11 x 11 (or 10 x 10) inch baking tray, line with parchment paper or baking sheet, grease some oil on it with a brush.
In a large bowl, mix egg yolks, vanilla extract, sugar, cooking oil and fresh milk together with a hand whisk, mix well and add in sifted flour, mix well again, set aside.
Whisk egg white to foamy and add sugar, continue to whisk egg white to smooth peak form at medium speed.
Take out 2 tbsp egg yolk mixture and 2 tsp egg white mix with little rose pink coloring and pipe dots on baking tray, using a skewer dragged outward from the center to create your own pattern and put in preheated oven at 170C for 1 minute.
Then fold 1/3 of the egg white to the egg yolk mixture, fold well with a rubber spatula and fold in the remaining egg white.
Make sure the baking tray is completely cooled down before pouring the plain mixture into it. Level the surface
Gently knock the tray on table top to remove air bubbles trapped in the batter and bake for 15 mins.
Turn cooled sponge onto a plastic sheet. Gently peel off baking sheet from the bottom of sponge and invert the sponge with skin facing up. Trim one end on a 45 degree angle and trim the other end on a similar angle. Spread an even layer of strawberry jam over top of sponge.
Gently roll up the sponge to make a Swiss roll. (place a tea towel underneath to prevent plastic sheet slip) Wrap with plastic sheet or cling wrap and chill it for one hour.