Prepare egg whites by separating from yolks and letting them sit at room temperature for 30 minutes.

Sift almond flour and confectioners' sugar together at least twice; set aside.

Whip egg whites with cream of tartar until foamy, then gradually add granulated sugar and whip until stiff peaks form.

Gently fold the sifted dry ingredients into the meringue until a smooth batter is achieved.

Pipe 1.5-inch circles of macaron batter on a lined baking sheet and let sit until a skin forms, about 60 minutes.

Bake in a preheated oven at 300°F (150°C) for 19-23 minutes; allow to cool completely on baking sheet.

Make ganache by warming heavy cream, then pouring it over chocolate morsels and butter. Whisk until smooth; fold in crushed Cadbury mini eggs.

Assemble macarons by piping ganache onto one shell and topping it with another; refrigerate overnight.