In a large mixing bowl, cream together the butter and sugar until well-combined. Sprinkle the salt over the butter. Slowly add in the flour, about ½ cup at a time, while mixing to incorporate it into the butter.
Form the cookie dough into a large ball, wrap it in plastic wrap, and refrigerate for 10 minutes, until chilled.
Preheat your oven to 325 degrees Fahrenheit (163 degrees Celsius).
On a lightly floured surface, roll the chilled dough out to a thickness of 1/4". Then, cut the dough into cookies and transfer them to an ungreased baking sheet. Sprinkle with sparkling sugar.
Finally, bake for 20-25 minutes until golden brown.
Notes
Store Sparkling Shortbread Cookies in an airtight container at room temperature for up to 2 weeks to maintain freshness. For longer storage, freeze them in a freezer-safe container for up to 3 months.Thaw at room temperature when ready to eat; reheating isn't necessary. However, if desired, briefly reheat in an oven preheated to 300 degrees F (150°C) for 5-10 minutes. Avoid overheating to maintain their texture.