In a small bowl, mix the confectioners’ sugar, cream, and salt with a spoon or rubber spatula until well blended and smooth. Add food coloring or flavorings, if using, and stir until well blended. The glaze should be thicker than heavy cream but still thin enough to spread and drizzle without clumping. If necessary, add more cream a drop at a time to adjust the consistency.
To drizzle with glaze: Arrange the cooled cookies on a rack. Use a fork to drizzle the glaze over the cookies.
To dip in glaze: Dip the side of each cookie to cover half or more of
the cookie. Let excess glaze drip off and then transfer to a rack. For drop cookies, you can also dip just
the tops in the glaze.
If you're adorning your cookies with additional decorative toppings, such as dragées or sanding sugar, add the toppings while the glaze is still wet. Let sit for about 10 minutes, then invert the cookie to remove any excess topping.
Let the cookies sit on the rack until the glaze is fully set, about 3 hours.
To pack glazed cookies: Arrange the cookies in snug single layers between parchment or waxed paper in a cookie tin or box.
The glaze can be refrigerated with plastic wrap pressed directly onto its surface for up to 3 days. Bring to room temperature before using.