Preheat the oven to 250°F and line a large baking sheet with parchment paper or a Silpat mat. Set aside.
In the clean bowl of a stand mixer fitted with the whisk attachment, whip the egg whites on medium speed. Make sure the bowl is clean of any fat or residue that could inhibit the egg whites.
4 large egg whites
Add in the granulated sugar slowly, about 1 tablespoon at a time. It should take 2-3 minutes to add all of the sugar.
1 cup granulated sugar
Once all of the sugar has been added, turn the speed to medium-high and beat until stiff peaks form, another 1-2 minutes.
Scoop the meringue mixture into a piping bag fitted with the tip of your choice. Pipe the mixture into 3-inch diameter discs onto the baking sheet and use a spoon to create a well in the center of each meringue.
Bake for 1 hour, or until the meringues are firm and dry but not browning on top.
Turn off the oven and leave them to cool insid, about 1-2 hours.
While the meringues cool, add the softened butter to the bowl of a stand mixer fitted with the paddle attachment and beat until it becomes smooth and fluffy. Add the powdered sugar and heavy cream and beat on medium speed until the mixture becomes smooth and creamy. Make sure to scrape down the sides a few times.
4 tablespoons unsalted butter, 1 cup powdered sugar, 2 tablespoons heavy cream
Transfer the buttercream to a piping bag and pipe it into the center of the meringue nests. Top with a few mini eggs and serve immediately.
10 ounces mini candy-coated chocolate eggs