In a stand mixer, with the paddle attachment, cream together the softened butter, granulated sugar, and salt until it looks wonderfully light and fluffy. Give it about 2 minutes to get perfectly airy.
Next, add in the eggs one by one, followed by the vanilla and almond extract. Mix until everything is just combined and smooth.
Slow the mixer down to its lowest setting, then gradually add the flour. Mix until the flour is just incorporated into the dough. Be careful not to overmix; gentle is key!
Take your beautiful dough and place it between two sheets of parchment paper. Use a rolling pin to gently flatten it out to about 1/8 inch thick. Transfer this flattened dough (still covered!) onto a cookie sheet and pop it into the fridge for 20 minutes to firm up.
While the dough is chilling, preheat your oven to 350°F (175°C) and line a cookie sheet with fresh parchment paper. Now, use your Linzer cookie cutters (one plain circle/heart, one with a small heart cutout in the center) to cut out your cookies. Remember to make an even number of plain cookies and heart-cutout cookies!
Carefully place your cut-out cookies onto the prepared cookie sheet. For best results and to ensure they keep their lovely shape, place the cookie sheet into the freezer for just 3-5 minutes before baking. Bake for 8-10 minutes, keeping a close eye on them. The edges should stay light, not brown.
Let the baked cookies cool completely on a wire rack. This is important for handling! Once cool, gently dust the powdered sugar over the cookies with the heart cut-outs. Then, spread a thin layer of your chosen jam onto the flat side of the plain cookies.
Carefully place a powdered-sugar-dusted heart cookie on top of a jam-covered plain cookie, sandwiching them together to create a delightful treat.
Store your finished Linzer cookies in an airtight container in the fridge for up to a week to keep them tasting their best!