
Preheat the oven to 180°C/350°F (160°C fan-forced). Grease a 23 x 33cm / 9 x 13" metal pan with butter (not a glass or ceramic one, and do not line with paper).
Dry ingredients - Whisk the flour, baking powder and salt in a bowl. Set aside.
Beat eggs 10 minutes - Put the eggs, sugar and vanilla in the bowl of a standmixer fitted with the whisk attachment. Beat on medium high for 10 minutes - it will become pale yellow and fluffy. (Or use an electric beater on high for 10 minutes - just alternate arms if they get tired!)
Add flour mixture and milk - Reduce the speed to low. With the mixer going, slowly add half the flour mixture, then all the milk, then remaining flour mixture. Stop beating as soon as most of the flour is incorporated. Then use a rubber spatula to mix the batter, scraping the base well, just to ensure everything is properly combined. Don't mix unecessarily long, you will deflate the batter!
Bake - Pour the batter into the prepared pan. Bake for 25 minutes or until a skewer inserted into the centre comes out clean. Cool 30 minutes before poking and soaking.
Whisk the 3-Milk ingredients in a large bowl or very large jug (1.5L/quarts) until the condensed milk is mixed through.
Poke - Use a thin chopstick, poke lots of holes all the way down to the base of the pan. I do around 130 - 13 rows of 10!
Soak - Slowly pour the milk mixture all across the top in about 3 additions, giving it a minute or two between pours so it has time to soak in rather than pooling. Pour with even soaking coverage in mind - eg if it is pooling on the sides because the cake is sloped, concentrate more on the centre and pour slowly.
Refrigerate at least 4 hours, or even overnight, to allow the milk mixture to disperse throughout the cake.
Whip cream - Beat the cream, sugar and vanilla using the stand mixer (whisk attachment) or electric beater until it is firmly whipped.
Cream and cinnamon - Spread the cream all over the top of the cake. (If you stabilise the whipped cream, you can top with cream the day before. I use McKenzie's Cream Stabiliser for this). Sprinkle with cinnamon - do this from a height using a fine sieve, for the most even coverage.
Cut into 12 very generous or 20 sensible pieces. Serve out of the pan.