Using a stand mixer, beat the butter and sugar on medium speed until smooth, about 1 minute.
Add the salt, orange zest, vanilla and egg yolk and mix until incorporated, about 1 minute.
Add the flour and mix on low speed until the ingredients just begin to come together. There will still be visible bits of flour. Finish mixing by hand with a rubber spatula, then fold in the cranberries.
Split the dough in half and shape each half into a disc shape. Cover tightly with plastic wrap and refrigerate dough for at least 2 hours.
Preheat oven to 350 degrees and line baking pans with parchment paper.
Remove one disc from the refigerator and let it sit at room temperature until it's soft enough to roll, but still cold and firm, about 20 minutes. Roll the dough between two sheets of wax paper until 1/4 inch thick.
Remove the top layer of wax paper and use 2.5" round cutter to cut out cookies, dipping the cutter in flour as needed to prevent sticking. Place cookies on the pan about 2 inches apart. Gently press together scraps and reroll to use up the remaining dough. Be careful not to overwork your dough. If it ever gets too soft, simply put it in the fridge for a few minutes to firm up. Repeat process with second disc.
Bake for about 10-12 minutes, until slightly pale on the edges. They will still look very light on top. Let the cookies set for 1 minute before transferring to a cooling rack to chill completely.
While the cookies are chilling, melt the chocolate. Bring 2 inches of water to a simmer in a saucepan. Place a heatproof bowl on top of the saucepan over the simmering water. The water should not be touching the bowl. Add the white chocolate and butter to the bowl and stir occasionally while the chocolate melts. Transfer melted chocolate to a bowl.
Dip each cookie into the chocolate, letting excess drip off before placing back on the rack. Before the chocolate is set, sprinkle with sparkling sugar.
Store in an airtight container for up to one week.