In the bowl of a stand mixer with the paddle attachment, cream together the butter and the sugar until light and fluffy (2-3 minutes).Beat in the lemon zest, lemon juice, and vanilla extract. Beat in each egg, one at a time.
Whisk together the dry ingredients (both flours, spices, baking soda, and salt) in a separate mixing bowl. With the mixer on low speed, add the dry ingredients to the wet ingredients a cup at a time, beating until well incorporated.
Dump the dough out onto a clean, floured surface. Divide the dough into four, shaping each into a disk. Wrap these in plastic wrap and chill in the fridge for at least an hour (or overnight).
Roll & Cut
Heat the oven 375 degrees F and prepare two baking trays with a layer of parchment paper.
Working with one ball of cookie dough at a time so that the remaining dough remain cold, roll the dough out on the floured surface to about a quarter inch thick. Cut out larger round circles and transfer them to the baking trays. Use the smaller cookie cutter to remove a center from half the larger rounds to make the top halves of the linzer tarts. Make sure each baking sheet has an even number of tops and bottoms, so that the cookies on the tray bake evenly and can be easily paired up with eachother.
Leave a space of 1-inch between all of the dough circles. Chill the filled baking sheet in the freezer for at least 20 minutes.
Bake
Bake the trays of cookie tops and bottoms in the oven for about 12 minutes. Check halfway trough and swap the position of the trays from top to bottom. When cooked through and lightly golden, remove from the oven.
Wait 10 minutes, then transfer the cookies to a cooling rack. When fully cooled, pair up each bottom cookie with a top cookie approximating the same size.
Fill & Dip
To fill the cookies, spoon a half teaspoon or so of raspberry jam onto the middled of each “bottom” cookie, spreading it out but leaving a wide margin at the edges. Place the corresponding top cookie over the jam, gently pressing the two together until flush, Some of the jam will pucker out of the hole in the top of the cookie. Chill the cookies for at least 30 minutes.
Prepare trays with parchment paper. Traditionally, you would stop here, dusting the cookies in powder sugar. Instead, melt the chocolate in a double boiler over medium light heat, Dip one edge of each sandwich cookie into the chocolate, and then either dip the cookie in sprinkles OR sprinkle the sprinkles onto the chocolate coating, pressing them down to make sure they stay in place as the chocolate hardens.
Chill or freeze, and eat in either 5 days at room temperature, or 3 months frozen in the freezer.
Notes
Stopping Points: It’s so easy to break up this recipe over multiple days if you need to. The dough can be chilled overnight or frozen for up to 3 months. Once the cookies are baked, you can wait to fill and/or dip the cookies for a day if the cookies are left at room temperature, or they can be frozen at either stage for up to 3 months. So while there are a few steps to the recipe, there is no imperative to get them all done on one day.Fitting Together Sandwich Cookies: When baking sandwich cookies like this, you might be tempted to do a whole tray of tops with the center window removed, and a whole tray of bottoms. I urge you not to. Each cookie sheet is going to cook slightly differently. There is a better chance of finding good matches between tops and bottoms if they are on the same baking sheet.Choosing Your Cookie Cutters: You can make Linzer tarts like these with any round cookie cutter, one large and one small. I recently found a Linzer tart specific cookie cutter with interchangeable center shapes, and I'm quite happy with how it worked out.