Step 1: Prepare the dough

1. In a large mixing bowl, beat the softened butter and powdered sugar until light and creamy.

2. Add the egg yolk, vanilla extract, and optional almond extract. Mix until smooth.

3. In a separate bowl, combine the flour and salt.

4. Gradually add the dry ingredients to the butter mixture, mixing until a soft dough forms.

5. If the dough is too crumbly, add milk a teaspoon at a time.

6. Shape the dough into a disc, wrap it, and refrigerate for 30 minutes.

Step 2: Shape the cookies

1. Preheat the oven to 175°C (350°F). Line a baking sheet with parchment paper.

2. Roll the chilled dough on a lightly floured surface to about ¼ inch (6 mm) thick.

3. Cut out 48 shapes using a round or festive cookie cutter. For half of the cookies, cut a small star or circle in the center to create a window.

4. Arrange the cookies on the baking sheet, leaving about 1 inch between them.

Step 3: Bake

1. Bake for 10–15 minutes, depending on the size, until the edges are lightly golden.

2. Let the cookies cool on the tray for 5 minutes.

3. Transfer to a wire rack and cool completely.

Step 4: Add the jam filling

1. Stir the jam until smooth. If it is very thick, warm it gently for a few seconds, then let it cool slightly.

2. Spread approximately 1 teaspoon of jam onto the flat side of each whole cookie.

3. Lightly dust the window cookies with powdered sugar.

4. Place a window cookie on top of each jam-covered cookie, pressing gently to sandwich them together.

5. Allow the jam to settle before serving.