2 tablespoons heavy whipping cream, 35% (plus extra)
2 tablespoons cornstarch or pudding mix
1 teaspoon salt
1 teaspoon clear vanilla extra
1/2 teaspoon clear almond extract
2 lbs powdered sugar
To make cupcakes:
Preheat oven to 375F (non-convection). Prepare a cupcake pan with liners.
Add the sugar and lemon zest to the bowl of a food processor, then pulse until the zest is broken up and the sugar is pale yellow in color.
In a large bowl, sift together the flour, baking soda, baking powder, and salt. Whisk together and set aside.
In a med-large bowl, manually whisk together the eggs, milk, melted butter, lemon juice, sour cream, lemon sugar, and vanilla extract. Add the wet mixture to the sifted dry ingredients and mix until just combined. Do not overmix.
Fill cupcake liners about 3/4 full. Bake for 5 minutes at 375F, then reduce temperature to 350F and bake another 10-12 minutes or until the springy to the touch and a toothpick inserted in the middle comes out clean.
Note: If you are using tulip-shaped cups like mine, check for doneness at the 9-10 minute mark after reducing the temperature to 350F.
To make lemon curd:
Cream together the butter and sugar in the bowl of a stand mixer. Add in eggs one at a time, mixing well to combine. Mix in lemon juice and lemon zest. Transfer to a medium saucepan. Cook over medium-low heat, whisking constantly until the mixture thickens and bubbles about 5 to 6 minutes. Transfer to a bowl and cover with plastic wrap touching the surface, then refrigerate overnight.
Using a cupcake corer or a paring knife, make a hole in the middle of each cupcake, reserving the removed top. Fill with lemon curd, and replace the reserved top piece, trimming to fit flat if needed.
To make buttercream:
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter for 30 seconds. Add in the heavy whipping cream, pudding mix/cornstarch, and salt, and combine but do not overmix to avoid incorporating too much air. Add in the vanilla and almond extracts. Scrape the bowl as needed. Add the powdered sugar in two batches, combining without overmixing. It will look dense at this stage but avoid adding more liquid. Whip for 2 full minutes, then assess to make sure it is not too stiff or gritty. Add 1-2 tbsp of cream or milk to adjust only if absolutely necessary. Divide into bowls, colour as desired with gel food colour, and separate into piping bags with desired tips.
Piping with the Russian tips can be a bit tricky, and the buttercream consistency can make it easier or more difficult. If you find the buttercream is too soft, add more powdered sugar. If it’s too stiff, add more cream. The piping tips that are most forgiving are the non-Russian ones.