Combine the 1 ¾ cups powdered sugar and almond flour in a fine-mesh sieve. Sift the mixture into a large bowl twice to ensure there are no lumps. Discard any large almond pieces that remain in the sieve to ensure smooth macaron tops.
In a clean glass or metal bowl, beat the egg whites and cream of tartar on medium speed until soft peaks form. Gradually add the granulated sugar one tablespoon at a time, increasing the speed to high. Continue beating until stiff, glossy peaks form that do not droop when the whisk is lifted.
Gently fold the dry ingredients into the meringue using a spatula. Use a “cut and fold” motion, scraping the sides of the bowl. Continue until the batter reaches a “lava-like” consistency, where it flows slowly off the spatula in a continuous ribbon without breaking.
Transfer the batter to a piping bag fitted with a round tip. Pipe 1.5-inch circles onto baking sheets lined with parchment paper. Tap the trays firmly on the counter several times to release air bubbles. Let the shells sit at room temperature for 30-45 minutes until a “skin” forms and they are no longer sticky to the touch.
Preheat your oven to 300°F (150°C). Bake one tray at a time for 12-15 minutes. The macarons are done when they have risen to form “feet” and do not move when lightly touched. Allow them to cool completely on the baking sheet before attempting to remove them.
Whip the softened butter, 1 ½ cups powdered sugar, vanilla, and heavy cream together until light and fluffy. Pipe a small amount of buttercream onto the flat side of one shell and sandwich it with another shell of similar size.
Melt the white chocolate wafers in the microwave in 30-second intervals until smooth. Transfer to a small piping bag with a tiny hole snipped off. Drizzle the chocolate back and forth across the top of the assembled macarons to look like bandages. Quickly place two candy eyes onto the wet chocolate before it sets.