Combine the confectioners sugar and almond flour in a fine mesh sieve and sift together into a bowl. Set aside.
Beat the egg whites at medium speed until foamy, and then add the sugar. Continue to whip at medium speed until stiff and glossy.
Take 1/3rd of the egg whites and add to the sugar-almond mixture, until it is all moistened, and then fold in the remaining egg whites. The mixture will loosen and deflate. Fold until it is a sticky batter, like a boxed cake mix. Separate into four bowls. Tint each one with a different color and stir inches Transfer to piping bags.
Cut 1⁄4 inch opening into pastry tip, and then pipe mounds the size of a quarter, at least two inches apart. Pipe the entire sheet pan in desired colors before moving to next step.
Rap the pan to release any bubbles. Pipe small dollops to create pusheen’s ears onto each macaron. Go back over each with a toothpick, and refine the shape.
Allow the macarons to dry for a minimum of 30 minutes, until they have a dull outside shell. If it is humid, it may take longer.
Bake the macarons, one sheet at a time, in the center of the oven for 12 minutes. Rotate halfway through cooktime. Remove and allow to cool before removing.
To decorate, combine confectioners sugar and water. Tint royal icing in desired colors and pipe onto macarons. Decorate pusheen designs onto half of the macarons.
Assemble the macarons by piping 1 teaspoon buttercream onto flat side of the undecorated macarons. Sandwich together with decorated faces.
TIP: Dry near a fan or air conditioner to speed process.