Apple-Loaded Shortbread Cookies with Apple Cider & Mascarpone Frosting

From Chef Dave Martin, New York City. Yield: 4 dozen cookies.

Apple-Loaded Shortbread Cookies:
1 lb unsalted butter, room temperature 
1 ¼ cups granulated sugar
1 ¼ tsp. vanilla extract
4 ¼ cups all-purpose flour, sifted
2 tsp. kosher salt
1 ⅓ cups Empire apples*, skin on, small dice
*Or similar variety

Apple Cider & Mascarpone Frosting:
8 oz. mascarpone cheese, right out of fridge
6-8 oz. confectioner’s sugar, sifted
4 oz. unsalted butter, softened
¼ tsp. vanilla extract
1 Tbsp. apple cider
¼ tsp. ground nutmeg 
½ tsp. sea salt

For apple-loaded shortbread cookies: In stand mixer, add butter and sugar. Blend with paddle attachment or electric beaters until mixture is light yellow.

Add vanilla. Sift in flour and salt. Add small pieces of apple and continue blending, using hands, until incorporated.

Remove dough, use a little flour (if needed), and work into a long roll (dough log). Wrap dough in plastic and chill for 45-60 minutes until butter sets.

Pre-heat oven to 350º F. Remove dough from cooler. Slice into ½" circles and place onto ungreased baking sheet. Bake for 20 minutes, or until golden. Remove from oven and cool. Cookies will harden as they cool.

Top with frosting.

For apple cider & mascarpone frosting: In stand mixer fitted with paddle attachment, or with electric beaters, mix mascarpone, powdered sugar and butter on low speed until incorporated.

Whip for a few more minutes until mixture is light and fluffy. Add apple cider, vanilla, nutmeg and sea salt. Occasionally turn mixer off and scrape sides of bowl with rubber spatula.

Store in refrigerator until somewhat stiff, about 30-45 minutes. Serve with Apple-Loaded Shortbread Cookies.