In the bowl of a stand mixer, combine the room temperature butter, powdered sugar, and salt. Using the paddle attachment start to cream the ingredients on low for 2 minutes, then gradually increase the speed to medium high and beat just until light and fluffy.

Add the flour and Matcha or sweet potato powder, and mix on low very carefully until everything is just combined and the color is mixed in. It's ok if it's a tad marble-y, you can incorporate more by hand as you push the dough together to wrap it and I think the purple especially looks cool with a bit of a marble loos. (You don't want to over-mix the dough if you want tender cookies.)

Pour the dough out onto a big piece of plastic wrap and form a round, disc. DIvide the disc in half and wrap each half with plastic wrap. Chill in the refrigerator at least an hour or freeze up to a couple months. (Double wrap the dough if freezing.)

When you’re ready to roll and cut the cookies, remove the dough from the fridge and place on the counter. (If frozen, place in the refrigerator overnight, then let soften a bit on the counter.)

When the dough isn’t rock solid, roll one disc out between two pieces of parchment paper and cut the cookies out using your monster shape of choice. Place the cut out pieces of dough on a parchment lined cookie sheet in the refrigerator to chill for a few minutes before baking. The rest of the dough can be re-rolled as needed. Repeat with the other disc.

When ready to bake, sprinkle the tops of the cookies with a little granulated sugar then bake in a preheated 350F/ 180C degree oven for about 10-12 minutes until the edges are just starting to turn golden. (Larger cookies may need a few minutes more to bake.) Let cool on the cookie sheet, then move to a cooling rack.

In a small bowl whisk the confectioner's sugar and water. You want to create a glue like consistency to stick the eyes and pipe the mouths. You don't want it too runny. Add a little more powdered sugar if necessary. Transfer the icing to a piping bag or zip-top bag.

Snip a very tiny end off the piping bag or zip-top bag and pipe two dots for the Matcha monsters or one dot in the middle for the PPE's. Stick the candy eyes on and use the rest of the icing to pipe some mouths. Let them dry if transporting or enjoy right away. (If you want to transport a lot of them or want them to be more stable, you can certainly use a royal icing which will dry harder than this simpler icing.)