1 ½cupsall-purpose flour,spooned and leveled (plus extra for rolling the dough)
¼tspcoarse Kosher salt(if using table salt, use half the amount)
¾cupcold unsalted butter,cut into 12 pieces
2tspvanilla bean paste or vanilla extract
2tbspmilk or cream
2tbsppowdered sugar, for dusting on top(preferably "non-melting" powdered sugar)
Make the cookie dough.
In your food processor, pulse the flour, almond flour, powdered sugar, salt and cardamom until combined.With the processor running, drop in the pieces of butter, one at at time, pulsing a few times until the butter is evenly distributed, and the dough is moistened and crumbly.Add the vanilla, almond extract and milk, then process until the dough starts to stick together.
Dump the dough out onto a clean counter and use your hands to finish bringing the dough together, kneading in any stray bits of flour. The dough should be soft, smooth and supple.
Shape the dough into a flat disk, wrap in plastic wrap, and refrigerate for 20 minutes, or up to an hour if the dough seems too soft for rolling.Prepare two baking sheets by lining them with sheets of parchment paper.
Roll and cut the dough.
Cut the dough in half, and just work with half at a time. Place the dough on a lightly floured surface and dust the top of the dough with flour, too. Roll out to an even thickness of 1/8 inch thick, using more flour as needed to keep the dough from sticking to the counter and your rolling pin.1/8 of an inch might seem too thin, but since they will be assembled into sandwich cookies, you don't want the cookies to be too thick and dense.
Use any size/shape cookie cutters to cut as many cookies as you can, placing the cut cookies 1-2 inches apart on the parchment lined baking sheets. Gather up the scraps of dough, roll them out again, and continue cutting as many cookies as you can.Using a 2 1/2 - 3 inch round fluted cookie cutter, you'll get about 42 cookies from this recipe (which will make 21 sandwiched linzer cookies.
Now take your smaller cookie cutter and cut out the centers of half of the cut cookies. You can add the centers to the dough scrap pile to cut more cookies.
Place the baking sheets with the cut cookies in the refrigerator and chill for 30 minutes. Chilling the cut cookies helps to ensure they don't spread and hold their shape perfectly while baking.
Bake the cookies.
Preheat the oven to 350F.Bake the chilled cookies on the center oven rack for about 8-9 minutes. The tops should be a very pale golden with no dark browning, and you should see tiny flaky layers around the edges. If you (very carefully) turn a cookie over with a spatula, the bottom should have light golden browning, with no appearance of raw or wet dough.This is NOT a cookie that you want to under-bake, since a doughy, under-baked shortbread cookie does not have a pleasant texture. So be sure your cookies are fully baked.
Cool the cookies for 5 minutes on the pan, then very gently transfer them to a cooling rack to cool completely. Shortbread cookies are delicate when warm, so handle with care. The cookies will initially be slightly crisp around the edges, but they soften as they're stored and will remain wonderfully soft and buttery.
Take the bottom cookies and turn them over so the bottom side is facing up.Spread about 1 - 1 1/2 teaspoons of jam onto the bottom cookies, but don't spread it all the way to the edge.
Lay out the top cookies (with the centers cut out) and lightly dust them with powdered sugar.Take the top cookies and set them on top of the jam, pressing down gently.
You can bake the cookies in advance, store them in an airtight container, and freeze for 3-6 months until you're ready to assemble them.
Wait until the day you're ready to serve your cookies to assemble and fill them with jam, since the jam will cause the cookies to soften as they sit. Even soft, they're still delicious, though. If you have any leftover filled cookies, store them in the refrigerator in an airtight container for up to 1 week.