In a saucepan, combine filling ingredients. Cook over medium heat for 5-7 minutes, or until thickened and translucent, stirring constantly. Remove from heat. Cool completely. Set aside.
Cookies
In a large bowl, combine butter & powdered sugar. Beat until light & fluffy. Add flour, orange zest & salt. Beat on low until a soft dough forms. Cover with plastic wrap. Chill 1-2 hours or until firm.
Baking
Preheat oven to 350 F. Line a baking sheet with parchment paper.
Shape dough into 1-inch balls & place on lined baking sheet 2-inches apart. Flatten balls with the bottom of a glass; dipping glass in granulated sugar to prevent sticking. Using a fork, prick top of each cookie making 3 rows.
Bake for 10-12 minutes or until edges are light golden brown. Cool completely.
Fill & Decorate
Spread about 1/2 tsp filling on bottoms of half of the cookies. Gently press bottoms of remaining cookies against filling to for ‘sandwiches’. On the top of each sandwich put a drop of remaining filling. Carefully lay two (towel dried) mandarin orange segments on it to form a butterfly.