• Prepare two rimmed baking sheets with macaron mats or parchment paper with 1-inch circles drawn underneath.
• Prepare a piping bag with a large round tip, like a #12. Place the piping bag in a tall drinking glass with the bag opening folded over or use a piping bag holder to keep it open. Place a small binder clip on the bag above the piping tip so the batter does not flow through the tip when filling the bag later.

Make the Macaron Shells

• Sift together the oat flour and powdered sugar into a medium sized bowl, then set it aside.
  126 grams oat flour, 126 grams powdered sugar
• In the bowl of a stand mixer fitted with the wire whisk attachment, beat the egg whites until foamy, then add the cream of tartar. With the mixer still running, add the granulated sugar one spoonful at a time.
  100 grams egg whites, ¼ teaspoon cream of tartar, 90 grams granulated sugar
• Add the vanilla and blue food coloring and continue to beat the whites until the meringue has formed stiff peaks.
  1 teaspoon vanilla extract, blue food coloring gel
  
• Fold ⅓ of the flour/powdered sugar mixture into the meringue. Then, add the rest of the dry ingredients and continue to fold and carefully press the batter against the sides of the bowl until the batter reaches just before the figure 8 stage. See note below on "macaronage."
• Transfer the batter to the prepared piping bag. Remove the binder clip, if using, to allow the batter to flow into the tip.
  
• Pipe 1-inch circles of batter onto the first macaron mat.
• Slam the tray down on a flat surface several times to cause air bubbles to rise to the surface. Use a toothpick or scribe tool to pop any large bubbles and smooth the batter over the hole.
• Repeat this process with the second tray. You will not fill the entire second tray.
• Let the shells dry at room temperature for 40 minutes. While they dry, preheat the oven to 300°F.
  
• Bake the shells for 12-15 minutes, rotating once after 7 minutes. I recommend baking one tray at a time.
• Remove the pan from the oven. Allow the shells to cool on the mat completely before removing them.
  

Make the Buttercream Filling

• In standing mixer fitted with the whisk attachment, beat butter and salt at medium-high speed until smooth, about 20 seconds. NOTE: If using a hand-held mixer, increase mixing times by at least 50%.
  10 tablespoons salted butter, 1 dash table salt
• Add powdered sugar and beat at medium-low speed until most of the sugar is moistened, about 45 seconds.
  5 ounces powdered sugar
• Scrape down bowl and beat at medium speed until mixture is fully combined, about 15 seconds; scrape bowl, add heavy cream and vanilla extract, and beat at medium speed until incorporated, about 10 seconds.
  1 tablespoon heavy cream, 1½ teaspoons vanilla extract
• Increase speed to medium-high and beat until light and fluffy, about 4 minutes, scraping down bowl once or twice. This step is important to create a smooth and whipped buttercream.

Fill and Decorate the Macarons

• Tap a small amount of gold edible glitter onto each shell. Use a food grade paint brush or your index finger to evenly distribute the glitter over the surface of the shells.
  
• Pair up the macaron shells by size to ensure the bottom and top of each macaron are similar in size.
• Fit a piping tip such as a #6B large open star tip into a piping bag. Add the buttercream to the bag. Pipe a mound of buttercream into the center of the bottom shell. Holding the top shell by the edges, place it on top of the filling and carefully press together. You can press straight down, or twist when you press down to change the direction of the pattern the buttercream will make.
  
• Immediately sprinkle the buttercream with the white sanding sugar so it sticks. Shake off the excess.
  
• Repeat with the remaining pairs until all of the macarons are filled.
  
• To add a buttercream snowflake on top, transfer some buttercream to a piping bag fitted with a small round tip, like a #5. If you prefer a thinner snowflake, you can use a #3 or #4. Carefully pipe a snowflake pattern on the top side of some of the macarons. Immediately after piping the buttercream, sprinkle it with white sanding sugar and place a white sugar pearl in the center.