Make sure the cupcakes are completely cooled before decorating.
Beat the softened butter until smooth, creamy, and noticeably lighter in color.
Gradually add the powdered sugar and mix on low speed until incorporated.
Add the vanilla extract, salt, and 2 tablespoons of cream or milk. Beat until smooth and fluffy.
Adjust the consistency as needed. Add a little more liquid if the frosting is too stiff or additional powdered sugar if it is too soft.
Add gel food coloring if desired and mix until the color is evenly distributed.
Fit a large star piping tip into a piping bag and fill the bag about halfway to two-thirds full with buttercream.
Twist the top of the piping bag and hold it firmly closed.
Pipe a steady swirl over each cupcake, starting around the outside and gradually moving toward the center.
Finish the swirl by reducing pressure and lifting the piping tip straight up.
Add sprinkles or other toppings while the buttercream is still soft.
Serve immediately or store the decorated cupcakes in a covered container.
