Day 4 and I save one of the most difficult for last. Once mastered, these cookies are delicious, however, after 4 batches, I ended up with only 4 or 5 aesthetically pleasing cookie sandwiches. Nevertheless, they taste just as well crumbled and cracked and broken. Here’s my first tip- when the recipe says teaspoon heaps, they mean it. I was very liberal with my first batch and the result was a solid sheet of sugary pecan candy. I always use my Silpat, which makes removing cookies from cookie sheets so easy, but in this case, parchment paper worked much better. The frosting, with the orange juice and zest, is delectable, and I can think of many uses for it in the future.

Cookies:

• 1/4 cup (1/2 stick) unsalted butter, room temperature
• 1/3 cup sugar
• 2 tablespoons light corn syrup
• 1/3 cup all purpose flour
• 1 cup coarsely ground pecans (about 4 ounces)
• 1 teaspoon vanilla extract

Filling:

• 1 cup powdered sugar
• 1/4 cup (1/2 stick) unsalted butter, room temperature
• 1 tablespoon orange juice
• 3/4 teaspoon grated orange peel

For cookies:
Position rack in center of oven and preheat to 350°F. Line 2 baking sheets with parchment paper. Stir butter, sugar, and corn syrup in heavy medium saucepan over low heat until melted and smooth. Bring to boil over medium-high heat, stirring constantly. Remove from heat. Stir in flour. Add nuts and vanilla; stir to combine.

Drop dough by teaspoonfuls onto prepared baking sheets, spacing 2 inches apart. Bake cookies, 1 sheet at a time, until bubbling and lightly browned, about 11 minutes. Cool on sheets 10 minutes. Transfer to rack; cool completely.

For filling:
Whisk all ingredients in medium bowl until smooth. Spread 1 teaspoon filling onto bottom of 1 cookie. Top with second cookie, bottom side down, pressing lightly to adhere. Repeat with remaining cookies. (Can be made 2 days ahead. Store between sheets of waxed paper in airtight container at room temperature.)