In a large bowl, mix together the dry ingredients. Set aside
In a separate large bowl, cream together the butter and sugar with a hand mixer
Add in the egg and vanilla and mix with a rubber spatula until combined
Add in dry ingredients and mix until a dough is formed
Dye the dough into desired colors and shape the cookies
Chill the cookies 15 minutes in the refrigerator
Bake at 375F/190C for 12 minutes
Let cookies cool then decorate with royal icing