In a stand mixer, combine melted butter, granulated sugar, vanilla extract, orange zest, and juice. Mix until well combined. Add the egg and mix on low.
Gradually add in the flour, cornstarch, baking soda, and salt while mixing on low. Mix until just combined. Cover the bowl and chill the dough in the refrigerator for 30-60 minutes.
Preheat the oven to 350°F. Line a cookie sheet with parchment paper. Using a medium cookie scoop, form 24 dough balls (about 2 tablespoons each). Roll them in granulated sugar and place 1-2 inches apart on the prepared sheet.
Bake for 9 minutes or until the cookie edges are set. Let them cool on the sheet for 5 minutes before transferring to a cooling rack.
Once completely cooled, melt white chocolate in a heatproof bowl, heating in 20-second intervals and stirring in between. Drizzle the melted chocolate over half of the cookies and top with sprinkles if desired.