Classic birthday cake (hot milk sponge layers with chocolate frosting)

Whisk together the flour, baking powder and salt; set aside.

In a mixer fitted with the whisk, beat the room-temperature eggs, sugar and vanilla about two minutes to ribbon stage: lighter in colour, increased in volume, the trail of batter sits on top a couple of seconds before dissolving.

Switch to the paddle, scrape down the bowl, add the dry ingredients all at once and stir until combined; scrape the bottom and sides again so no pockets of sugar or leavener remain.

Bring the milk to a simmer in a pot on the stove; add the butter and oil and stir until the butter melts.

With the mixer on low, pour the hot milk mixture into the batter and mix until combined; the batter will be thin. Scrape down.

Line the pans with parchment rounds (or parchment traced and cut to the pan) and divide the batter equally between the two pans.

Frosting: stir the natural cocoa with some confectioners sugar and the salt; add vanilla, then hot water, and mix to a smooth paste.

Add the rest of the confectioners sugar and the unsalted butter; start the mixer on low, then beat on high until fluffy, lighter in colour and smooth.

Test the baked layers: golden brown and even on top, pulling away from the sides, springs back when pressed in the centre, a toothpick comes out mostly clean.

Cool in the pans about 15 minutes, run a spatula or butter knife around the edge, invert, remove the pan and parchment, and cool completely on a rack.

Optional: trim just the very top skin off each layer to level it and prevent a gummy layer.

Dab frosting on the plate or turntable to hold the cake, tuck scrap parchment strips under the edge, add a generous scoop of frosting on the first layer and set the second layer on upside down for a flat top.

Crumb coat: spread as little frosting as possible over the top and down the sides, scrape off the excess, and chill about 15 minutes.

Final frosting: frost the top generously and bring it down the sides, then make swoops with the back of a spoon.

Remove the paper strips, add sprinkles, and move the cake to a serving plate with a big offset spatula; add candles.