This cookie just says … it’s beginning to look a lot like Christmas!
Sift together the flour, baking powder and salt. Cream the butter and sugar until light and fluffy. Add the eggs, one at a time, and beat until smooth. Beat in vanilla. Beat in the dry ingredients just until dough holds together. Form the dough into two flat rectangles. Cover tightly with plastic wrap. Refrigerate for 30 minutes.
Preheat oven to 350 degrees F.
Line baking sheets with parchment paper.
On a lightly floured surface, roll one rectangle of dough to 1/4-inch thickness. Using 2 to 3-inch cookie cutters cut out as many cookies as you can. Place on parchment-lined baking sheets, at least 1-inch apart.
Cut out tops using same cookie cutters from rolling the second rectangle of dough, again to ¼-inch thickness. Then cutting out a window in each of these cookies with a smaller cutter or tip of knife. Place on separate parchment lined baking sheets, at least 1-inch apart. Re-roll the dough left over from cutting out the windows for additional cookies, ensuring that you have an equal amount of cookie tops and bottoms. Sprinkle top cookies with coarse sugar, if desired.
Bake cookie tops and bottoms until firm and as they just turn golden around edges, about 8 to 12 minutes.
Let cookies cool on the baking sheet for 5 minutes (this will help them crisp up and make them less fragile when transferring the cooling rack). Using a metal spatula, transfer the cookies onto a rack to cool completely.
Spread jam or lemon curd in centre of bottom cookies and sandwich with top (window) cookies. Dust with icing sugar, if desired. Makes 40 sandwich cookies.