In a mixing bowl, whisk together the flour, baking powder and salt.
In another large mixing bowl or in the bowl of a stand mixer, cream together the softened butter and the sugar until it is smooth and a pale yellow color.
Add the egg and vanilla extract to the creamed butter and sugar and mix until it's all combined.
Pour the dry ingredients into the wet ingredients and mix them all together until it forms a wet dough and there are no dry pockets of flour left.
Form the dough into a disc (a flattened ball) and wrap it in plastic cling wrap. Refrigerate the dough for at least one hour, or overnight.
Remove the dough from the fridge. Lightly flour a clean work surface and roll out the dough until it's about ¼-inch thick. Preheat the oven to 350°F
Cut out shapes using your cookie cutters and place the cut-out shapes onto a baking sheet lined with parchment paper or a silpat. Once you cut out shapes in the rolled-out dough, form the dough back into a ball, roll it out again, and cut out more shapes.
Bake your cookies for about 10 to 12 minutes, until the edges start to turn the lightest shade of golden brown. Move the cookies from the baking sheet to a wire cooling rack and cool them completely before decorating them.
Decorate with Royal Icing
Sift the powdered sugar into a large mixing bowl or the bowl of a stand mixer.Add in the egg white and 4 tablespoons of water.Begin whisking with a hand mixer or begin mixing on a low speed with the paddle attachment on a stand mixer.
If the icing looks and feels too thick to be able to pipe onto cookies, add another tablespoon of water and a time, until it's your desired texture.
Add a few dollops of the icing into a small bowl and cover the rest of the icing with plastic cling wrap so it doesn't dry out. Mix in gel food coloring to your bit of icing that was separated into a small bowl. For my Easter cookies, I used black, purple, orange, yellow, green, pink and purple gel food coloring. For the white, I just didn't add any coloring, as the icing is naturally white.
Pour your dyed icing into a piping bag and go to town! Repeat with separating a few dollops of icing into a small bowl, dyeing it, adding in into a piping bag, and decorating your delicious cookies.