For the cookies: Sift flour, baking powder and salt into a bowl and give it a little stir to combine. Set aside.
Cream butter and sugar together with an electric mixer until light and fluffy. Add egg and vanilla and mix until smooth. Slowly add the flour mixture to the butter mixture and mix just until combined.
Note, if the dough is still too sticky, add another ¼-1/3 cup flour until no longer sticky.
Transfer dough to a lightly floured surface, knead briefly to bring it all together. Flatten dough into a disc, wrap in plastic wrap and chill for at least 2 hours.
When dough is chilled, preheat oven to 325F (170C). Line a baking tray with baking paper. Roll the dough out on a lightly floured surface to ¼-inch thick. Use your cookie cutter of choice to cut out shapes from the dough, dipping the cutter into some flour after each cut. Re-roll the dough as necessary.
Place cookies on prepared tray and bake 6-10 minutes, depending on the size of your cookies (smaller cookies need less time, larger cookies need more time).
Remove from the oven when the edges of the cookies are just starting to brown. Cool on tray for 5 minutes, then transfer to a wire rack to cool completely.
For the icing: Sift icing sugar into a bowl. Add butter, vanilla extract and sufficient boiling water to mix to a spreadable/pipeable consistency. For different icing colours, divide the white icing in separate bowls, then add one drop at a time of red colouring to icing to get shades of colouring, light pink to dark red.
I piped the icing onto the cookies, using a small round tip. I traced around the edge of the cookie first, then filled it in. Feel free to make designs, or simply spread it on. Allow the icing to set 30-60 minutes. Note that this icing does not set hard.
Depending on how large your cookies are, and how much icing you'd like to put on the cookies, you may need to make double the amount of icing.