In a large mixing bowl, cream together the shortening and granulated sugar for 2-3 minutes until light and fluffy. Add the eggs and milk and mix to combine.
Place the flour, baking powder, and salt in a separate mixing bowl. Whisk until fully incorporated.
Add the dry ingredients to the wet mixture a little at a time, mixing between additions. Mix just until the dough is formed. Finally, mix in the vanilla extract.
Chill the dough for at least 1 hour before rolling it out. When rolling out the dough, cover your surface with flour to keep your dough from sticking. With a rolling pin, roll out the dough (about ½ inch thick) and cut out the cookies.
Preheat oven to 325°F and line a cookie sheet with parchment paper. Place cookies on the lined baking sheet and bake for 12 minutes or until the edges are slightly golden brown. Let them cool completely (10-15 minutes) before frosting.
FOR THE FROSTING
In a large mixing bowl, cream together the butter and shortening until light and fluffy (2-3 minutes). Add the powdered sugar one cup at a time, mixing between additions. Mix in the vanilla extract.
Add in the milk or heavy cream as needed. Add food coloring if desired. Frost your sugar cookies and enjoy!
Notes
Avoid overmixing your ingredients. After adding the flour, mix just until the ingredients are fully incorporated.
Allow the cookie dough to chill for at least an hour so it can easily be rolled and cut out.
Let the cookies cool completely to room temperature before frosting them. This keeps the frosting from melting and getting too runny.