1. Combine confectioners sugar and almond flour in a food processor. Pulse until blended and finely ground. Line 2 large baking sheets with parchment paper. Heat oven to 350 degrees .
2. Whip egg whites and salt in a stand mixer on medium-high speed until frothy. Gradually beat in granulated sugar, 1 tbsp at a time, until stiff peaks form, about 2 minutes.
3. Fold one-third of the confectioners sugar mixture into beaten whites. Fold in remaining confectioners sugar mixture and the food coloring. Transfer to a large piping bag (use half the batter so bag is not overfilled) and snip off a 1/2-inch opening.
4. Pipe batter in 11/4-inch circles onto parchment paper. Let stand at room temperature for 15 to 20 minutes.
5. Bake cookies, 1 sheet at a time, at 350 degrees for 15 minutes. Cool completely on paper on wire racks.Ganache
6. Place chopped chocolate in a small bowl. In a small saucepan, heat cream just until steaming. Pour over chocolate and stir until smooth. Refrigerate until good spreading consistency.Filling
7. Beat butter until smooth. Add confectioners sugar and salt; beat on low speed until blended. Add heavy cream and beat until good spreading consistency. Divide in half; tint half orange with gel food coloring.
8. Carefully remove cookies from parchment. Spread ganache or white or orange filling onto flat side of a cookie. Sandwich with a second cookie. Repeat with all cookies.