1. Measure out all ingredients precisely using a kitchen scale.

2. Sift the almond flour and powdered sugar together twice into a large bowl. Discard any large bits of almond that don't pass through the sieve. Set aside.

3. In the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites on medium-low speed until foamy. Add the cream of tartar (if using) and gradually increase speed.

4. Once the egg whites form soft peaks, slowly add the granulated sugar, a spoonful at a time, while continuing to beat on medium-high speed.

5. Continue beating until the meringue is glossy, stiff, and holds firm peaks (this can take 8-10 minutes). If using gel food coloring for the shells, add it during the last minute of whipping until fully incorporated.

6. Add about one-third of the dry ingredient mixture to the meringue. Fold gently with a rubber spatula using a "cut and fold" motion, scraping the sides of the bowl, until just combined.

7. Add the remaining dry ingredients in two more additions, folding until the batter reaches the "macaronage" stage. This means the batter should flow like lava, creating a "ribbon" when lifted with the spatula, and slowly melt back into itself in about 15-20 seconds. Be careful not to overmix.

8. Transfer the macaron batter to a piping bag fitted with a round tip.

9. Line two baking sheets with silicone mats or parchment paper. Pipe 1.5-inch rounds, leaving about 1 inch between each macaron.

10. Firmly tap the baking sheets against the counter 2-3 times to release any trapped air bubbles. Use a toothpick to pop any remaining visible bubbles.

11. Let the piped macarons rest at room temperature for 30-60 minutes, or until a skin forms on top. You should be able to gently touch a shell without batter sticking to your finger. This is crucial for developing "feet."

12. Preheat your oven to 300°F (150°C) with an oven rack in the middle position. An oven thermometer is highly recommended.

1. Bake one sheet at a time for 12-15 minutes, rotating halfway through. The macarons are done when they have developed "feet" and don't wobble when gently touched. They should peel easily off the mat.

2. Let the baked shells cool completely on the baking sheet before removing them. They will be fragile when warm.

1. While the shells are cooling, make the buttercream. In the bowl of a stand mixer, beat the softened butter on medium speed until creamy, about 2-3 minutes.

2. Gradually add the sifted powdered sugar, about 1 cup at a time, mixing on low speed until combined, then increase to medium.

3. Add the heavy cream, vanilla extract, and a pinch of salt. Beat on medium-high speed for another 3-5 minutes until the buttercream is light, fluffy, and smooth.

4. If desired, add a tiny speck of yellow or orange gel food coloring and mix until combined.

5. Gently fold in the finely crushed Cadbury Mini Eggs using a spatula. Be careful not to overmix, as the candy coating can melt slightly.

1. Once the macaron shells are completely cool, match them up by size.

2. Transfer the Cadbury Mini Egg buttercream filling to a piping bag (with or without a tip, depending on desired aesthetic).

3. Pipe a generous dollop of filling onto the flat side of one macaron shell.

4. Gently top with a matching shell, twisting slightly to evenly distribute the filling.

5. Store the assembled Cadbury Egg Macarons in an airtight container in the refrigerator for at least 24 hours to "mature." This allows the shells to soften and meld with the filling, improving texture and flavor.

6. Bring to room temperature for 15-20 minutes before serving for the best taste and texture.