Jam Pinwheel Cookies

Instructions

• LINE 2 large baking sheets with parchment. Set aside.

• STIR flour with salt in a medium bowl. Beat butter with mascarpone and icing sugar in a stand mixer on medium-high, until pale and fluffy, 4 to 5 min. Beat in egg yolks and vanilla, scraping down sides of bowl if needed, until smooth, about 1 min. Reduce speed to low. Gradually add flour mixture until combined. Scrape dough onto a lightly floured counter and divide in half. Using a floured rolling pin, roll each piece to 1/4 in. thick. Trim edges to make a 12-in. square. Roll onto rolling pin and transfer to a prepared baking sheet (dough may go up sides of sheet). Freeze until firm, 15 to 30 min. Repeat with remaining dough.

• PREHEAT oven to 350F. Stir egg whites with water. Remove dough from freezer. Slice dough down the middle, both ways, to make 4 squares. Slice each square down the middle, both ways, to make 4 more. You should have 16 squares. Arrange squares on baking sheets 1 in. apart. With a sharp paring knife, make a 1 1/2-in. cut diagonally from each corner of each square toward the centre (do not cut all the way to the centre). Dab corners with egg white. Spoon 1 tsp jam in the centre of each square. Fold every other corner tip of dough into the centre to form a pinwheel, sealing with egg whites and pressing tips to hold together. Repeat for all squares. Brush tops of cookies with egg whites, then sprinkle with coarse sugar.

• BAKE in centre of oven, until cookies are golden, 20 to 22 min. Let cookies cool on sheets 1 min, then transfer to a wire rack to cool completely. Repeat with remaining dough and jam. Store cookies in an airtight container up to 1 week or freeze at least 1 month. (Prep tip: Dough must be very cold in order to get perfectly straight edges. Return dough to freezer to chill as needed.)