Step 1: In a large bowl, cream together the softened butter and powdered sugar until light and fluffy.
Step 2: Stir in the orange zest and salt until well combined.
Step 3: Gradually add the flour, mixing just until a soft dough forms.
Step 4: Shape the dough into a disk, wrap in plastic, and refrigerate for 1 hour.
Step 5: Preheat oven to 325°F (165°C) and line a baking sheet with parchment paper.
Step 6: Roll out dough to 1/4 inch thickness and cut into shapes. Place on the baking sheet.
Step 7: Bake for 12-15 minutes or until the edges are very lightly golden. Cool completely on a wire rack.
Step 8: Melt the dark chocolate (and coconut oil if using) in a microwave-safe bowl. Dip half of each cooled cookie into the chocolate and place on parchment paper to set.