In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter, confectioners’ sugar, and salt on high speed until the mixture becomes light and fluffy. Pause to scrape down the sides of the bowl, then add the vanilla extract. Reduce the mixer speed to low and gradually incorporate the flour until the dough just comes together.

Transfer the dough onto a sheet of plastic wrap, shape it into a tight log or disc, and wrap it securely. Flatten slightly and refrigerate for at least one hour, or until the butter has firmed up. If you're short on time, you can place it in the freezer to speed up the chilling process.

Once chilled, roll the dough out to about ½ inch thick. For best results, roll it between two sheets of parchment paper to prevent sticking—this also avoids the need for extra flour, which can make the cookies dry.

Use a 2-inch round cookie cutter to cut out the cookies and place them on a parchment-lined baking sheet. Gather the remaining dough scraps, roll them into a ball, and repeat the rolling and cutting process until all the dough has been used.

To form the thumbprint indentations, press the center of each cookie gently using a ½ teaspoon measuring spoon to create an even, circular well (alternatively, you can use your thumb). Make sure the indentation is deep enough to hold a generous amount of filling. If the dough becomes too soft or sticky, refrigerate the sheet tray briefly to firm it up before continuing.

Refrigerate the shaped cookies for at least 30 minutes before baking. While the dough chills, preheat the oven to 350°F (175°C). Once ready, bake the cookies for 25–30 minutes, or until the tops are just turning golden. Remove from the oven and allow them to cool completely to room temperature.

To prepare the filling, whisk together the Biscoff spread and heavy cream in a small bowl until smooth and creamy. Transfer the filling to a piping bag or a plastic zip-top bag with the corner snipped off. Pipe the filling into the cooled thumbprint centers of each cookie.