In a large bowl, cream together the butter and the sugar until pale and fluffy, about 2 minutes.

Next, add the eggs one at a time, followed by the vanilla. Mix until just combined. 

In a separate bowl, stir together the flour, baking powder, and salt.

Add the dry ingredients into the creamed butter and mix until a dough is formed.

Lay some cling wrap on your counter and spoon your dough on top and form a log about 17 inches long. Roll up the log like a sausage and chill the dough for at least 1 hour or pop in the freezer and freeze for up to 8 weeks.

Preheat your oven to 350°F (180°C). Line 2 cookie sheets with parchment paper and set aside. 

Slice the cookies around ¼ inch thick. Place the cookies about 2 inches apart on the prepared cookie sheet.

Bake for roughly 10-12 minutes or until slightly golden. Remove from the oven and allow to cool completely on a wire rack. 

Using a whisk, combine the powdered sugar, butter, milk, and vanilla until you have a smooth thick icing. Color the icing with a few drops of food coloring then mix until even in color. 

Using a small offset spatula or the back of a small spoon frost the cookies then scatter over sprinkles. Allow setting for about 30 minutes.

Once set, cover and store the cookies in an airtight container for up to 2 days.