Preheat your oven to 375 F and line a cookie sheet with parchment paper
Mix the butter, sugar and lemon zest until just smooth.
Mix in the egg yolk, beat 30 seconds.
Add in the flour and salt and mix, the dough will look crumbly but come together when pressed together.
If it is hot where you are then chill the dough for 30 minutes
Generously flour your surface and dump out your dough, press togehter, lightly kneading to create a smooth flour. Depending on where you are you may want to add more flour.
Roll out the dough about ¼ inch thick and cut with cutters of choice.
Bake till the edges are golden - 10 minutes for medium sized cookies, adjust for smaller or larger ones.
Knead dough again, roll and cut cookies until it is used up
Let the cookies cool completely before icing.
If using a royal icing mix follow package decorations for a stiff icing then gradually (very gradullay, drops of water at a time) add enough water that the consistency is toothpaste like. A spoonful dropped back into the icing should disappear in 15 seconds. Tap the bowl gently on the counter to deflate air bubbles.
If making royal icing then mix the icing sugar, milk, salt and vanilla on low speed until just combined, adjust the thickness by adding more icing sugar or water to get the consistency described above.
To decorate the cookies you can put your icing in a squeeze bottle or a piping bag and do a smooth white base. You can also gently dip the tops of the cookies in a bowl of icing and let it set. Use a skewer to pop any air bubbles.
Icing mixes tend to set in a few hours, homemade royal icing needs to sit out overnight.
When it is time to paint bring out your icing colors, put them on a plate or palette, take a deep breath, give your kids brushes and smile :)
Dough: I find the dough tastes better with the egg yolk as a binder but you can absolutely make it without too.
No Cutters? No problem: My cutters are from With a Spin, but you can totally cut out shapes with a glass, your kids (washed) play doh cutters or let your kids shape them by hand!
Decorating Note: If you do not want to deal with royal icing then melt ½ cup chocolate chips or candy melts, take out the sprinkles and let the kids drizzle away. Lemon zest works well with melted white chocolate or vanilla candy melts. If you're using regular chocolate chips then omit the lemon and add ½ tsp of vanilla extract.