Orange creamsicle cake

Orange curd: whisk the granulated sugar, cornstarch and flour together in a medium pan.

Whisk in the freshly squeezed orange juice until there are no lumps, then the four egg yolks, reserving the whites.

Cook over medium to medium-low, whisking continuously, about five minutes until it comes to a boil and thickens; go by texture, not temperature.

Once boiling, cook one additional minute, stirring, until it coats the back of a wooden spoon and holds a trace.

Whisk in the salted butter until it disappears, pour into a bowl, lay parchment on the surface and chill about two hours.

Preheat the oven to 350 with two racks towards the centre. Sift the flour, baking powder and salt into a large bowl and whisk.

Beat the softened butter, orange zest and sour cream on medium about a minute until combined.

Add the granulated sugar in three additions, then run on high about two minutes until light and fluffy.

Add the eggs one at a time on medium, scraping down two or three times.

Add the flour mixture in three additions alternating with the orange juice on the lowest speed, then finish mixing by hand, scraping the beater and the bowl.

Divide the batter between three buttered, parchment lined and floured 8 inch pans and wrap damp cake strips around the edges.

Bake about 30 minutes, rotating the pans at 20 minutes, until the centres are springy and a skewer comes out clean.

Italian buttercream: put the granulated sugar and water in a heavy bottomed saucepan; put the egg whites in the stand mixer with the whisk attachment and have the third of a cup of sugar and the four cups of softened butter ready.

Heat the syrup on medium high, stirring until the sugar melts, then stop stirring once it is clear and boiling; brush the sides down with a wet pastry brush.

Run the mixer on medium high and pour in the third of a cup of sugar slowly, whipping to soft silky peaks.

Bring the syrup to the soft ball stage, 235 Fahrenheit, and no hotter than 240.

Pour the hot syrup slowly into the egg whites while the mixer runs at medium speed, aiming into the whites.

Increase to high, add a quarter teaspoon of salt and run about 10 minutes until the meringue is room temperature.

Add the butter a tablespoon at a time; it will look like soup until the last of it goes in.

If it stays liquid, chill the bowl 5 to 10 minutes and whip again, then add the vanilla.

Assemble: a cup of frosting as a base on the first layer, then about half the curd, another layer, more frosting, the remaining curd and the final layer, reserving three tablespoons of curd for the top if you want a pool.

Smooth a paper-thin crumb coat over the cake and chill it while the colours are mixed.

Divide the remaining frosting into four bowls plus reserved white; melt a drop of gel food colouring into each in the microwave for 10 seconds, mixing less colour into each successive batch for a gradient.

Pipe two or so rings of each colour around the cake darkest at the bottom, plop the white on top, pre-smooth with a small offset spatula cleaning the tools between colours, then smooth with a bench scraper on a turntable.

Re-whip the remaining frosting, load a big piping bag with a large open star tip and pipe a rope pattern round the top edge.

Melt the reserved three tablespoons of curd in the microwave in 10 second bursts with a teaspoon of butter, pour into the centre, smooth towards the edge and set in the fridge about 30 minutes.