For the Custard

1. In a small bowl, add drops of water to the cornstarch until you can stir it together to make a slurry (thick but pourable liquid).
2. Combine heavy cream and half the sugar in a small pot. Stir together egg yolks and the remaining half of sugar in a heat-proof bowl.
3. Bring heavy cream mixture just to a boil, then slowly drizzle into the egg yolk mixture while whisking constantly.
4. Once heavy cream is incorporated into egg yolks, whisk in the cornstarch slurry.
5. Pour the custard mixture back into the pot, and cook over medium-low heat, stirring constantly until bubbles break the surface. 
6. Strain into a clean bowl, and press plastic wrap on the top to cool.
7. Chill a couple of hours to set. 
8. Transfer the custard to a small piping bag or plastic baggie fitted with a small round tip, or simply snip the end to create a quarter-inch opening.
9. Store leftover custard in the refrigerator for a couple of weeks.

For Chocolate Ganache

1. Place the chopped chocolate or chocolate chips in a heat-proof bowl. 
2. Bring the heavy cream just to a boil in a small pot and pour it immediately over the chocolate. Let the hot mixture sit for five minutes. 
3. Whisk the cream and the softened chocolate together until smooth. 
4. Cool to room temperature.
5. Transfer the cooled ganache to a small piping bag or plastic baggie fitted with a small round tip, or simply snip the end to create a quarter-inch opening.
6. Store surplus chocolate ganache in the refrigerator for a couple of weeks.

For Vanilla Buttercream

1. With a hand mixer or a stand mixer with a whisk attachment, whip the butter on high speed for about three minutes, until it is light in color and doubles in volume.
2. In small increments to prevent a powdered sugar fog, beat in the confectioner's sugar (use more or less depending on how sweet you prefer buttercream). Beat the buttercream until it is light and smooth, scraping the bowl with a spatula as you go.
3. Beat in a pinch of salt, your chosen vanilla, and the heavy cream.
4. Transfer the buttercream to a small pastry bag or plastic baggie fitted with a quarter-inch or smaller round tip, or simply snip a tiny opening with scissors. You can always make the opening bigger, so start small. 
5. Store extra buttercream in the refrigerator. Bring to room temperature before using, and beat brielfy to restore a smooth texture. 

For Cadbury Creme Egg Macarons

1. Line two baking pans with parchment or silicone baking mats. Place printable egg macaron templates underneath. Preheat the oven to 300° F. Use an oven thermometer to ensure your oven is reaching the proper temperature. A too hot or underheated oven will cause issues with macaron appearance.
2. If using almonds, grind the nuts with confectioner's sugar in a food processor until finely ground.  If using almond flour, sift the almond flour with the confectioner's sugar onto a piece of parchment paper or into a large bowl. Set aside. 
3. Combine the egg whites and granulated sugar in the bowl of a stand mixer with a whisk attachment (or use a hand mixer).
4. Whip on high speed to a firm meringue, the meringue will be shiny and form peaks that curve slightly off the beater. 
5. Sift the ground almond mixture with the cocoa powder directly into the bowl of whipped meringue. 
6. Fold until the batter flows slowly and ribbons off the spatula. Mix firmly at first, then use classic folding strokes; scraping around the sides of the bowl, then up from underneath the mixture, and over through the top. The batter will be thick and take 15 to 20 seconds to settle back into itself when drizzled off of the spatula.
7. Transfer the batter to a piping bag (or large plastic bag) fitted with a small round tip.
8. Pipe the batter onto the parchment-lined baking pans with the egg template underneath as aguide. Hold the piping bag vertical, and about a quarter-inch above the pan. Begin at the narrow end of each printed egg, and move slowly toward the wide end making quick, side-to-side motions that gradually get bigger. When you reach and fill the largest part of the egg, stop squeezing and quickly flick your pastry bag away in a circular motion.
9. To help the tops of piped batter settle, very lightly tap the pan on the counter. Or with one hand, tap the underside of the pan a few times gently in a few places.
10. Optional: Let the piped macarons rest on the counter for 10-20 minutes. 
11. Bake 300° F for 12-15 minutes. Rotate the pans once halfway through baking. Macarons are done when the frilly feet have formed and the tops don't wiggle away from the bottoms when very lightly pushed. If macarons brown before they are set, turn down the oven by five or ten degrees and bake longer. 
12. Cool for a few minutes before removing macarons from the parchment paper or silicone mat. Gently remove the shells from the mat or parchment by pushing up from underneath the liner to release the bottoms. If the macarons resist and break when you try to peel them off the parchment or mat, more time in the oven was needed.
13. Take half of the macaron shells and pipe a perimeter of the vanilla buttercream slightly in from the edge. Pipe a dollop of the custard filling in the middle, and top with another egg macaron. For extra rich Cadbury egg macarons, pipe a perimeter of chocolate ganache first, then inside the ganache alternate with dollops of buttercream on the top and bottom, and custard in the middle. Avoid piping the filling too close to the edges of the shells, so it doesn't ooze out when bitten into. No matter how you arrange the fillings, the macarons will be absolutely sinful!
14. Store French macarons chilled for 24 hours before serving. The shells and fillings will soften slightly and the flavors will mature. But only if you can wait that long!