In a medium mixing bowl combine the flour, baking powder, and salt.

In the bowl of a stand mixer beat the butter until smooth. Gradually add in the sugar and continue mixing on medium until fluffy.

Add in the egg and vanilla and beat until mixed well.

Place the mixer on low and add in the flour mixture, mixing until just blended.

Knead the dough into a ball and flatten into a disc shape. Cover with plastic wrap and refrigerate for at least an hour.

Preheat the oven to 375 degrees.

On a lightly floured surface roll the dough to 1/4 inch thick. Cut the cookies using a 2 or 3 inch shamrock cookie cutter. Place the cookies on a baking sheet and bake for 6-8 minutes or until they no longer look wet on top.

Remove from the oven and allow to cool for 2 minutes on the cookie sheet before removing to a wire rack. Cool completely.

Mix all the royal icing ingredients in the bowl of a stand mixer. Mix on low for 3-4 minutes or until everything is well incorporated.

Add water a few drops at a time until icing is still thick, but is able to be piped. Divide into 2 bowls, tint one with green coloring and leave the other white.

Put into piping bag, and pipe the outline of sugar cookies. Keep unused icing covered so it doesn’t dry out .

To make icing the correct consistency for flooding, add water until the icing runs off the back of a spoon. Flood cookies using a toothpick to spread the icing. Let dry for 10 minutes then pipe on decorations.

Allow decorated cookies to dry overnight so that the icing gets hard.