Preheat oven to 325 degrees F.
In a small bowl, stir together milk and vinegar and set aside for a few minutes to sour milk.
In a small bowl, whisk together flour, baking powder and salt and set aside.
In a larger bowl, whip four room temperature eggs** until light and fluffy. Add sugar and mix well. Add soured milk and vanilla and mix.
Add 1/2 the dry mixture, mix until just combined. Add remaining dry ingredients and mix again until just combined. Don't overmix.
Spray a cookie sheet with non-stick cooking spray. Measure a piece of parchment paper to fit into the bottom of the pan, nestle it in and spray again with non-stick cooking spray.
Pour batter into pan and use an offset spatula to spread it evenly, right to the edges of the pan (thinner edges will cook faster and are more likely to burn).
Bake in preheated oven for 14-17 minutes. Watch edges closely to make sure they don't brown. If they do, cake is likely done. If you're not sure, insert a toothpick into the centre of the cake and if it comes out clean it's done.
While cake is baking, spread out a clean tea towel and sprinkle it with icing sugar. When cake is done cooking, invert it onto the tea towel (while still hot) and gently peel off parchment paper.
Starting at a narrow end, gently and tightly roll the cake and tea towel together up into a roll. Set on a baking rack to cool completely.