In a medium sized mixing bowl, cream the butter and then add powdered sugar and cream together with a hand mixer. Add orange liqueur and vanilla and continue to mix until smooth.
Add flour and orange zest to the bowl and work the two ingredients into the butter and sugar mixture using a spatula or your hands. Take care not to over-mix. You're going for well-combined, but not beaten.
Scoop the mixture into the middle of a piece of plastic wrap, mold into a log shape about 1 1/2 inches in diameter, then roll up in the plastic wrap and tie off the ends. Place in the freezer for 1 hour.
After the dough has hardened in the freezer, preheat your oven to 350ºF. Cut the dough out of the plastic wrap and cut in 1/8 inch think slices. Place on a cookie sheet covered with parchment and bake for 11-13 minutes or until the cookies begin to turn golden brown.
Allow the cookies 20 minutes to cool. Meanwhile, microwave your chocolate in a small microwave safe dish by heating in 1 minute increments at 30% power, stirring in between each increment. Continue to do this until the chocolate is melted - warm to the touch, but not hot.
Dip each cookie half-way into the chocolate and then place on a nonstick surface to harden. A silicone mat or parchment paper works well for this. Sprinkle the chocolate with fresh orange zest as desired. Enjoy once set.