Lemon Curd
1-Mix: Mix: In a small pan or pot, stir together the egg, egg yolks, sugar, and lemon juice.
2-Heat until thickened: Heat until thickened: Heat the mixture on medium-low heat, stirring frequently, until it thickens into a gel-like consistency, about 10-15 minutes. When you drag a spatula through the curd, it should part and take a few seconds to come back together.
3-Stir in butter: Stir in butter: Remove the pan from the heat and stir in the butter, one cube at a time, until they melt into the lemon curd before adding the next one.
4-Strain: Strain: Push the lemon curd through a fine mesh sieve to remove any bits of cooked egg or lemon seeds for a silky smooth texture. Transfer the lemon curd to a small bowl to cool at room temperature or in the fridge.

Cupcakes
5-Prep: Prep: Preheat the oven to 350°F. Line a 12-hole muffin pan with cupcake liners and set aside.
6-Mix dry ingredients: Mix dry ingredients: In a medium bowl, stir together the flour, baking powder, and salt. Set aside.
7-Heat milk mixture: Heat milk mixture: In a small pot or microwave-safe bowl, add the butter, milk, oil, and vanilla extract. Heat it on the stovetop or in the microwave just until the butter has melted. Don’t let it boil. Remove it from the heat and cover to keep it warm while you start making the batter.
8-Whip eggs: Whip eggs: In a large mixing bowl, add the eggs and sugar. Use an electric hand mixer fitted with a whisk attachment to beat the mixture on low-medium speed increasing to medium-high speed for 6 whole minutes until the egg mixture has tripled in volume and becomes very pale (almost white) in colour.
9-Mix in flour: Mix in flour: Add half of the flour mixture and mix on low speed until just barely combined. Add the rest of the flour mixture and mix again until just barely combined. Some flour patches in the batter and up the sides of the bowl are fine.
10-Stream in hot milk: Stream in hot milk: With the mixer on low speed, slowly stream the hot milk mixture into the batter with your other hand, mixing until just combined into a smooth, fluid batter.
11-Fill cupcake liners: Fill cupcake liners: Fill the cupcake liners about ⅔ full. Bake cupcakes for about 20-22 minutes or until a toothpick inserted in the middle comes out clean with a few crumbs and the tops spring back when gently pressed.
12-Cool: Cool: Let the cupcakes cool in the pan only for about 5 minutes before lifting them out of the pan and transferring them to a wire rack to cool completely.

Swiss Meringue
13-Create a double boiler: Create a double boiler: In a small pot, bring about 1″ of water to a boil. To a heat-safe mixing bowl that fits on top of the pot perfectly without touching the water, add the egg whites, sugar, and vanilla extract.
14-Heat mixture: Heat mixture: When the water comes to a boil, turn off the heat and place the mixing bowl on top of the pot. Gently heat the mixture, stirring often, until all the sugar has dissolved and the mixture is warm. If you rub a bit of the mixture in between your fingers, it should feel smooth without any grittiness.
15-Beat until stiff peaks: Beat until stiff peaks: Remove the bowl from the pot, being careful not to get any water in the bowl. Use an electric hand mixer fitted with a whisk attachment to beat the mixture on low-medium speed until it becomes foamy. Increase to medium-high speed and continue beating until the mixture becomes opaque white and stiff peaks that curl over slightly at the tips.

Assemble the cupcakes
16-Scoop out the middle: Scoop out the middle: Use a small melon baller or a knife to scoop out the middle portion of each cupcake, about halfway deep into the cupcake.
17-Fill with lemon curd: Fill with lemon curd: If you’ve stored your lemon curd in the fridge overnight, heat it in the microwave or stovetop for a more fluid and pipable consistency. Transfer the lemon curd to a piping bag and snip the tip of the bag off. Pipe the lemon curd into the middle of each cupcake.
18-Top with meringue: Top with meringue: With a cookie scooper, add a scoop of meringue on top of each cupcake or pipe it on top with a piping bag and piping tip. Use the back of a spoon to press a depression on top of the meringue to fill with lemon curd later (optional).
19-Torch meringue: Torch meringue: Use a kitchen torch to toast the meringue to your liking. Be careful not to get too close to the cupcake liners as they’re flammable. Add an extra dollop of lemon curd on top of the meringue if you like!